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funfly
12th Jan 2015, 17:39
Having just got a new petrol engined car I notice that I have two types of petrol to choose from, one normal price and one more expensive.

Said to girl in kiosk "Does anyone really buy the more expensive petrol?" to which she replied "Yes, quite a lot of people do".

So I ask fellow pPruners, a group with world wide experience on matters such as these, am I missing something by buying the basic petrol as against paying extra for the 'posh' grade?

What's it all about then?

FF

Espada III
12th Jan 2015, 17:47
Have a look at the Honest John (http://www.honestjohn.co.uk) site and the Forum section. Lots of comments both for and against. Some high performance cars need minimum 98 Octane. Some cars which do a low mileage of mainly stop start driving without getting fully warm may also benefit. Finally some drivers report smoother engines, improved 'pick up' and better economy. Many don't.

Fareastdriver
12th Jan 2015, 17:49
If my man tries to fuel the Roller with the cheap stuff it shuts the filler flap on his fingers.

G-CPTN
12th Jan 2015, 17:52
Isn't your roller diesel? :E

mixture
12th Jan 2015, 17:57
funfly,

Pretty much as hinted at by the others, if you're only driving a crummy old 1.6L banger, then its unlikely to make one iota of a difference to your life !

But the source of all knowledge is your car's manual .... if it says 98 Required, then thou shalt obey !

sitigeltfel
12th Jan 2015, 17:58
What's it all about then?

You need to ask a bloke called RON!

KenV
12th Jan 2015, 18:10
I'm not sure what the difference is in the UK, but in the US the only difference is in the octane rating. So long as the cheap stuff has the at least the octane rating required by your engine, buying the expensive stuff will make no difference other than to produce more expensive exhaust fumes.(the octane rating is required to be on the pump here in the US.).

This assumes the car is properly maintained and in tune. Older cars MAY have slightly higher compression than new ones due to carbon and other deposits building up inside the combustion chamber. Dirty injectors can result in a lean fuel-air mixture and out of tune ignition can result in slightly early ignition timing. Higher octane fuel MAY help (a little) in these cases.

rogerg
12th Jan 2015, 18:11
My other car is an MGTF and I use "Posh petrol. Just seems to go better and always passes the MOT emissions. Often "older" cars have a problem. Also made my MGB more fun.

Dr Jekyll
12th Jan 2015, 18:21
Go for the cheapest if you can, you will get more mpg.

Really? Why is that?

Lancelot de boyles
12th Jan 2015, 18:41
Go for the cheapest if you can, you will get more mpg.

er, not quite

Some cars need the higher RON value. It's stated in the book. simple. use it. One of my more exciting antique toys definitely works much better on it, judged by having had to run it a few times on lesser peon fuel, when supplies of big RON were pinched off.

Some cars will work fine with the lower value, but you will get better overall performance using the higher grade. Also stated in the book. One of my little runabouts does nicely on the cheap, when cruising gently. However, when it is used in a slightly more hooligan style, it certainly does better on the higher octane.
And in either case, the higher RON results in better MPG. While not a major gain, it easily offsets the cost.

Some cars don't care which grade goes in, so don't bother with the higher octane. However, peeing in ones own tank after a night in the local is probably taking it too far.

DType
12th Jan 2015, 19:25
I think that some cars are clever enough to cater for either normal or super octane, using the knock sensor to 'detune' the engine when on the lower octane. Even on the higher octane, I guess the engine will be held on the verge of detonation so as to get the most out of the fuel. Hence I can believe that the higher octane really can give more mpg.
Some additives are a cheaper route to higher octane than buying from the dear pump.
Anyway, I could never hear if the TVR was pinking over the exhaust noise, so it's super plus for it (or a squirt of the additive when in the back of beyond).

ShyTorque
12th Jan 2015, 19:34
Some of us who like to get the best out of our engines like to experiment with ignition timing. It's sometimes the case that manufacturers' settings are quite conservative and the sparks can be advanced a little. I've done this quite a few times and obtained better performance. When I do this I fill up with Super unleaded to prevent detonation.

I used to own a Nissan which had two ignition advance settings in the manual. The first, which was more retarded, was for unleaded petrol and the other was for 4 Star fuel. I used the vehicle for towing and when I did it needed the advanced setting and 4 Star to be any good.

Some Vauxhall cars had a reversible connector in the ignition circuit to allow the owner to easily change the ignition advance in similar circumstances.

vulcanised
12th Jan 2015, 19:45
There are many who add Acetone (BP not nail variety) to a tankful and swear it gives them better performance & economy.

Flybiker7000
12th Jan 2015, 20:50
I read Funfly's posting as regarding to the 'luxury brand' and not the RON difference!
Here in DK it's mainly Shell and Statoil who sells 'advanced' fuels, mostly under the promise of a little mileage-improvement.
My appraisal to the subject is that the max possible improved mileage in percent is more than half the percentage surcharge, hence the cost per mile wont improve!
As for the mileage, other mentioned improvements is likely vague and within the changes a rapid trip outside urban areas would do to the engines behaviour.
I consider it waste of money :-|

At the nearby refinery, I see tankers from all the oilcompanies refilling for deliverance to their individual gasstations and each of those with luxury brands manage to make the difference by adding a small shot of some wonder liquid into a 10.000 liter tank-compartment. With other words: It's not some clever chemestry during the cracking and refining of the crude oil but morely something comparable to the long exsisting 'Red-X' standing on the shelf at any gasstation!

Espada III
12th Jan 2015, 20:57
Allegedly the Shell diesel product with the high price uses gas to liquid technology which produces an even and clean burn to improve economy and clean the engine. Who knows. I use it occasionally and the car does seem to run a little smoother. Couldn't comment on economy.

TWT
12th Jan 2015, 21:03
I can choose between E10,91,95 or 98 RON unleaded at the filling stations.Will never use the E10 (91 +10% ethanol) version.Car accepts all of them,no appreciable difference between 91 and 95 so don't pay more for the 95.

Flash2001
12th Jan 2015, 21:11
You need to be a little careful here! (North America) Different states and provinces have different rules. Pretty well all standard octane motor gasoline is adulterated with 10% or so ethanol. Some high test gasolines, Shell V power for instance, is warranted not to have any ethanol in it. In some states some regular gasolines are warranted the same way. Most cars don't take any harm from the ethanol but they burn their fuel within a short time after purchase. Woe betide he who stores this witches brew! If the storage tank is vented the moisture absorbed by the ethanol forms a 3 phase mess at the bottom of the tank that corrodes the living hell out of the fuel system.

After an excellent landing etc...

Smeagol
12th Jan 2015, 21:13
Carried out a comparison between Regular Unleaded 95 RON and Super Unleaded 97 RON a while back in my previous car, a BMW 728 e38. I have always recorded the mileage and amount of fuel added (full to second 'click' on pump) so can easily calculate the mpg on a brim to brim basis rather than relying on the on-board computer.

Normally used the 95 RON fuel but for about 5 fills used the 97 grade and over similar usage there was no dicernible difference.............except to my wallet!

I believe the engine management system was able to adjust to suit as mentioned by others so unless using it to its absolute limits where the high rated fuel just might give some advantage (a few HP more?). But an elderly 728 is not the vehicle to play 'boy racer' in so was not realized.

Would therefore suggest that unless one has a high performance car and wish to extract the full potential from it...........save your money and use the cheapest fuel recommended for the vehicle.

Shaggy Sheep Driver
12th Jan 2015, 21:29
I use Shell Super Unleaded in my motorbikes as they seem to like it, and I think it lasts longer than the cheaper stuff when left in the tanks / injectors / carbs during low usage in winter.

Flybiker7000, I remember Fredericia refinery! Spent about a few days a week for several weeks in Fredericia in the late 1980s while doing some IT consultancy for Shell. It was a fun place to get to in those days; fly to Copenhagen from Manchester (BA, SAS, or Aer Lingus), passing over the refinery. Then to Billund (Maersk Air) passing over the refinery again. Finally, hire car to Fredericia.

ShyTorque
12th Jan 2015, 22:00
As is often the case, over generalisation isn't the best advice.

An engine with a very conservative ignition setting (i.e. not much advance and no knock sensor) might show no improvement with a higher quality fuel. But tweak the advance a bit more and that same engine could be quite a bit more lively, except that it might pink/knock at times. But give it a better fuel and the knock can be prevented so the improved performance can be safely used without risk of engine damage.

Not so easy to arrange with modern, ECU controlled engines. But still possible via "chip tuning" if the ECU can be reprogrammed.

Union Jack
12th Jan 2015, 22:34
Have a look at the Honest John site and the Forum section. - Espada

I'm definitely with Espada.:ok:

My long term reading of Honest John, not least his Q&A responses at "Ask Honest John" to questions regarding performance fuel makes it very clear that the use of Shell V-Power Nitro+, whether petrol or diesel, makes sufficient positive difference to fuel consumption to warrant the additional cost. All this quite apart from the fact that Shell V-Power Nitro+ contains more effective additives than any other readily available fuel. And, if you can't get Shell V-Power Nitro+in your neck of the woods, then he recommends the use of relevant petrol and diesel Ecomaxproducts sold by certain Mr Miller (with whom I have no more connection than I have with Shell, or Honest John for that matter).

As Honest John frequently points out, published performance figures are based on the use of the very best available fuel, together with the fact that engines are designed for their optimum running accordingly.

In conclusion, and for fun, here's a link to the questionShould my son use Shell V-Power in his Audi R8? | Ask Honest John | Honest John (http://www.honestjohn.co.uk/askhj/answer/48865/should-my-son-use-shell-v-power-in-his-audi-r8-) I can't quite run to an R8, but I can unreservedly assure anyone that's interested that the use ofShell V-Power Nitro+ has made a very impressive difference to the consumption, performance, smooth running, and overall driving pleasure of our two Jaguars.:)

Jack

PS And, no, I'm not John Prescott...:=

onetrack
13th Jan 2015, 00:05
The small gain from using premium fuel/s has to be weighed against the additional cost - which, here in Oz, is often a substantial difference in simple cents per litre.
At present in Oz, premium fuels are a complete and utter "rort" for oil companies and fuel resellers, with price differences between "regular" and "premium" fuels often being around 15%, or even more.
I'm convinced this is purely because it's generally the much more costly "luxury" or "performance" brands of vehicles, that require premium fuels in manufacturer recommendations, that makes the oil companies and fuel resellers think this "well-heeled" clique are quite oblivious to what they pay for their fuel.
In fact, I know more than one individual who cares little about what he pays for fuel, because "it's nearly all a tax-deduction, anyway" (he runs a business and all his vehicles are listed as "company vehicles".)

Interesting comments on this NSW motoring site - and most are based on "seat-of-the-pants feel", not carefully-regulated testing.

http://www.mynrma.com.au/blog/2007/10/02/using-premium-unleaded-petrol/

Loose rivets
13th Jan 2015, 00:44
"Thing" wanted posh fuel and indeed, posher oil. Vast quantity of Mobil 1 cost a bomb. If plebeian fuel was used, the computer cut back to punish one.


http://img.photobucket.com/albums/v703/walnaze/Cars/E500Sport001_zps0fcb9d3d.jpg (http://smg.photobucket.com/user/walnaze/media/Cars/E500Sport001_zps0fcb9d3d.jpg.html)


http://img.photobucket.com/albums/v703/walnaze/Cars/CarsatNaze083-Copy_zps3eff201c.jpg (http://smg.photobucket.com/user/walnaze/media/Cars/CarsatNaze083-Copy_zps3eff201c.jpg.html)

This 850 mini was breathed on by a Brightlingsea firm. They cut so much off the head they had to repair the oil duct in the head casting by brazing in some brake pipe. The result was >13:1 compression.

Bo-locks??!! Nope, very accurate gauge which I've just unearthed after 30 years. The car was quicker than the Jag to 50 but the most astonishing thing was the 50 mpg at 50 mph. Lean burn was the thing. However . . .

5***** ONLY. Not a chance of running on lesser juice. Also, a set of exhaust valves lasted 5k - on a good day. I got the lads at Mortons Air Services to get me a head gasket while I was flying and changed it by the AA?? RAC?? box across the Brighton road near the terminal. Got some street cred out of that.

The engine needed an anti-torque rod to save the mounts.

Tell the kids of today . . .

Eddie Dean
13th Jan 2015, 02:04
If I have deciphered loose Rivet's post, he is referring to higher compression ratios requiring higher octane fuel.
The Beast I drive is a retro 1970s with V8 carb engine, and similar to Mr Rivets I went a little overboard with decking the block, flat top pistons and a bit off the heads.
On a cool day will run on 95RON, depending on the fuel supplier, but no running on or preignition with 98RON.

The trick I have found, as others have alluded to, is to retard the timing if the octane rating is a bit low.

tdracer
13th Jan 2015, 02:45
A word of warning - if you have a high output and/or turbocharged engine, running less than the recommended RON is a high risk bet that saving a few cents/liter or gallon won't damage your engine - basically that the computer and knock sensor will compensate.
I lost that bet ~10 years ago. I had a Mitsubishi with a turbocharged 2 liter. Normally I'd fill up with the recommended high octane stuff, but if all I was going to do was interstate cruising I'd often buy 'mid-range' lower octane fuel. I burned a valve :eek:. In fact I burned two (although the second was just starting to go when I had to rebuild it).
I'm pretty sure the ~10 cents/gallon I saved was more than offset by the cost of the needed engine rebuilt :ugh::ugh::ugh:
I currently have two vehicles with high compression/high output engines - a Honda S2000 (240 hp from 2 liters :ok:) and a BMW 3 series - that recommend high octane fuel. Neither will ever see low octane "regular" fuel so long as I own them:=
BTW, avoiding ethanol in automotive gasoline isn't practical around here - it's pretty much required by law. Back during my racing days, I ran a 'spec' class for a while that required unleaded fuel. We had to buy the stuff at the track as it was the only place we could buy unleaded that didn't have alcohol in it (instant DQ) - at a time when we could buy 'premium unleaded' at the local gas station for ~$3/gallon, the stuff at the track went for $12/gallon :eek: - it actually cost more than the 110 octane leaded racing gas :ugh:

Solid Rust Twotter
13th Jan 2015, 05:29
I find the higher octane fuel around here (98) makes going up some of the steeper inclines far less noisy and a little faster.

Pinky the pilot
13th Jan 2015, 08:26
Used to drive a 1974 Toyota Celica with a 'somewhat worked' twin cam engine. (Modified head and 'three quarter race' camshafts; Totally gutless below 4,100rpm:eek:)

Did not like standard unleaded fuel (92 Octane) here in Australia one little bit.:ooh: Could only really use the Premium 98 octane stuff but really performed well when using 100/130 Avgas.:ok:

Years ago for a period of about 18 months I had a supply of Avgas which was cheaper per litre than the unleaded Mogas.:ok:

Still have that car but it has been off the road for nearly 5 years, undergoing a long term restoration project. And have a different engine to put into it once completed.

A 3TGTEU engine.:eek::E 1800cc Twin Cam, Two spark plugs per cylinder fuel injected Turbo Charged.

Yes!!!!!:ok::D:D

:ok::ok::ok::ok:

DType
13th Jan 2015, 09:03
Nowadays the ECU knows whenever you refuel (monitors the fuel gauge and/or filler cap), and can then select the appropriate engine map after monitoring the knock sensor for a mile or two. Or mabe just after every time you start the engine. So you should always get the best performance and economy for the current fuel.
Those micro processors do give some benefits - most of the time.

Skeleton
13th Jan 2015, 09:59
Onetrack, I agree the price hike on premium is a joke but put anything other than 98 in my Mazda and i notice a difference. My brother had it for a week insisted 91 was fine and it cost him a new fuel pump.

cattletruck
13th Jan 2015, 11:14
I've only ever known 2 types of fuel - vapours and audible low fuel alert.

Now that the price of fuel is poised to drop below $1/litre I may celebrate with a 3rd type of fuel in my cars 14 year history - a full tank...or maybe not.

The standard Aussie family car is actually a real fuel miser on highways regardless of what watered down crap you feed it. City driving is a different story so if you want real savings or more mpg around town then just reduce the weight of your fuel load by 40kg.

Loose rivets
13th Jan 2015, 11:23
A long time ago I posed the question on JB about retarding the ignition to stop, erm, pre-ignition.

Someone answered with a plausible theory, but not only do I not believe it, I've forgotten what he said. Thinks: How do I know I don't believe it if I've forgotten it?:confused:

Anyway, how does altering the timing stop PRE-ignition?

londonblue
13th Jan 2015, 11:51
I used to own a sports car, and would only fill it up with Texaco top grade petrol.

I could genuinely tell the difference. The car shifted far better with that in it than any other petrol.

These days I have a different car, and use any old diesel in it.

(As an aside, at the time I owned said sports car the sister of a colleague of mine used to work for Texaco. She said that the company were so impressed with this top grade fuel, and how it looked after car engines that they were considering giving people a warranty. I can't remember the full details, but it was something along the lines of, if you only use their fuel and the engine went on your car, they would replace the engine for you. They didn't do it because it would have been impossible to police properly.)

DType
13th Jan 2015, 12:11
It is not really pre-ignition, the burn starts at the spark time but instead of progressing through the mixture progressively the increaseing temperature and pressure "diesel" the remaining mixture explosively and prematurely.
At the other extreme, on high revving engines it can be difficult to complete a progressive burn in the time available for doing useful work.
So a rock and a hard place!

ShyTorque
13th Jan 2015, 12:43
It is not really pre-ignition, the burn starts at the spark time but instead of progressing through the mixture progressively the increaseing temperature and pressure "diesel" the remaining mixture explosively and prematurely.

I agree, it's called detonation.

Pre-ignition is slightly different, when the engine runs without power to the ignition circuit because something other than the spark is firing the mixture.

chuks
13th Jan 2015, 13:33
We have a 2002 BMW 330Ci. On its filler flap a sticker reads "UNLEADED PETROL ONLY ROZ/RON 91-98".

The engine ignition system, part of an integrated electronic engine management system that can do all sorts of clever things such as altering the valve timing, has some sort of knock sensor that advances or retards the ignition timing to accommodate higher or lower octane ratings.

It must be that the least amount of advance allows the use of the lowest octane fuel, which would obviously give a bit less performance than that yielded by maximum ignition advance. Given that my BMW is used for day-to-day driving and that it has more horsepower than it needs for that, I normally use 95-octane fuel with about 10% bio-ethanol added.

I know the car will redline in 5th on the Autobahn on 95-octane, at an indicated 250 km/h. That's probably an actual speed of approximately 130 mph (155 on the clock minus over-reading and tire slippage), which is fast enough for me.

I had some French jerk in a new Renault give me that "Out of my way, slow-poke!" flash of the high beams just as we had cleared the border with Luxembourg. (I was keeping a safe distance behind a Volvo in the left lane, waiting to go zooming off, first chance I had.) So I pulled over to let Super Frog past, when he tailgated the poor old Volvo driver without mercy, until he could pull over in turn having passed slower traffic. Then I pulled out and stayed with the Renault, which got up to around 220 or so and then pulled over to the right. Then I passed the Renault doing about 225 and waited for what I thought would happen next.

Sure enough, here comes Super Frog, obviously intent on formating on my rear bumper. So I just went to full throttle and disappeared. Every so often I would hit traffic and slow down until I could make a safe pass, when my little French friend would reappear. The first time that happened I pulled over and let him past, even letting him get some distance ahead. Then I overtook him again, doing about 240 on the clock, when he just shrank to a little black dot in the mirrors for a while. That was on 95-octane, 1.20 euro per liter in Luxembourg.

nonsense
13th Jan 2015, 14:03
When unleaded was introduced here in Australia in 1986, there was a significant drop in octane rating from the previous leaded "super" petrol. Quite a few cars sold soon after the change really did not appreciate this and tended to ping like crazy. In particular I've had experience with several 1986 Corollas which all pinged badly on standard unleaded.

The last one was a high mile example belonging to a friend a few years ago. He (an engineer) tried running it on high octane unleaded and found that the improved fuel consumption alone more than paid for the more expensive fuel as well as dramatically improving driveability.

Some GM (Opel/Vauxhall sourced) small cars here in the 1990s had two different ignition timing maps and a plug you could turn around to tell them which fuel you were using.

More recent cars often have a knock sensor and will adjust the timing to make the most of whatever you put in them.

If your motor is not intended to benefit from higher octane fuels, then it will not benefit; they don't contain more energy or provide more power, they simply allow a higher compression ratio and/or more advanced ignition, which is what will provide improved efficiency/power.

Your owner's manual should tell you what fuel to use, including whether you can use lower octane fuel and whether you need to do anything special.

If you're curious, you can always do as my friend did and run a few tanks of higher octane fuel to see if the consumption, power or driveability changes.

MG23
13th Jan 2015, 18:06
I'm not sure what the difference is in the UK, but in the US the only difference is in the octane rating.

In Canada, and I believe the US, too, they also load the cheap stuff up with alcohol which cuts your mpg by a significant amount and can destroy the engine if they use too much (>15% alcohol, AFAIR).

One reason we didn't buy the Turbo version of our new SUV is that we'd have had to buy the more expensive fuel that costs about $0.50 a gallon more. Though at least it's actually petrol and not diluted with alcohol.

Flybiker7000
13th Jan 2015, 21:50
'Late 80's'!
That was about that period I was employed at the construction of the then new condensing-line at the load-ramps.
It was at the same job that my colleague got himself the still used nickname: 'Dark Eager' due to at stressed explanation causing words to be mixed up :-)

G-CPTN
13th Jan 2015, 22:20
In 1966 I was running a full-race Lotus Seven as my (only) road car.

It needed 5-star petrol, and, on one occasion I inadvertently filled the tank with 2-star.
I realised immediately, and an MG TC pulled-in so I asked him if he could use some 2-star fuel. We drove to his house nearby and syphoned the fuel from the Lotus into his MG - I made a long-term friend (I refused to accept payment - and I later discovered that this was the most fuel that his MG had seen throughout his ownership).

When travelling on the motorway I frequently had vehicles catching me up and trying to travel in close convey - I just opened the tap and blasted ahead before returning to my conservative cruising speed (the fuel consumption was proportional to the road-speed) until the w4nk3r caught up again then I would have to leave them standing again (they never seemed to want to overtake and head off faster than me).

Windy Militant
13th Jan 2015, 22:21
Three pages and nobody's mentioned 5 star petrol, dunno what the world is coming to.

The Bruv had a K reg Honda 750 which used Five star had a big sticker on the Tank to remind you of that. He sold that one and bought an MGB to please a girlfriend, well we all do daft things don't we. Anyway a few years down the line the girlfriend left and he bought an R reg CB 750 this one ran on four star and then he bought a CB 900 FZ which ran on two star.
About this time I Had a Yam XT 500 which ran on Four star. On one occasion I ran onto reserve out in the sticks and the next Garage I came to only had Two Star. I bought Half a gallon to get me to the next Garage and rode very gingerly as opening the throttle even very slowly made her pink like a bas:mad:d. Thankfully they had Four Star at the next garage so I brimmed her with the stuff.

Loose rivets
14th Jan 2015, 01:52
Three pages and nobody's mentioned 5 star petrol, dunno what the world is coming to.



Apart from me, you mean?


5***** ONLY. Not a chance of running on lesser juice.

unstable load
14th Jan 2015, 06:14
I had a mildly warmed 'shovelhead' Harley
Does it have a weekly calendar instead of a monthly one??:}:E

nonsense
14th Jan 2015, 11:16
There are lots of potential problems with ethanol mixes, particularly with fuel system components corroding and with water being absorbed into the fuel.

Obviously the Brazilians solved this all many years ago, but the solutions cost money and not all vehicles are suited to even 10% mixes (E10), never mind higher.

Unless you're confident your car is intended to cope with ethanol, avoid the stuff like the plague.

Even if it is designed to withstand the problems ethanol can bring, the fuel consumption penalty outweighs the price benefit, at least at Australian prices. It's almost as if the ethanol were just filler, using nearly 10% more E10 than straight petrol appears to be quite common.

tomahawk_pa38
14th Jan 2015, 12:48
Sorry to take this off topic slightly but when I had new tyres fitted recently the garage tried to persuade me to pay extra to have them filled with 100 % nitrogen instead of air on the basis that they would be quieter and more efficient. Given that what we breathe is 75% nitrogen anyway this sound a money-spinning racket to me. Any views ?

bingofuel
14th Jan 2015, 15:42
G-CPTN

"- I just opened the tap and blasted ahead before returning to my conservative cruising speed until the w4nk3r caught up again then I would have to leave them standing again (they never seemed to want to overtake and head off faster than me)."

I find a much more enjoyable pastime to just progressively slow down, and find it amazing just how slow I can get before it dawns on the 'pursuing' driver and they eventually pull out and overtake.

KenV
14th Jan 2015, 16:02
In Canada, and I believe the US, too, they also load the cheap stuff up with alcohol which cuts your mpg by a significant amount and can destroy the engine if they use too much (>15% alcohol, AFAIR).

One reason we didn't buy the Turbo version of our new SUV is that we'd have had to buy the more expensive fuel that costs about $0.50 a gallon more. Though at least it's actually petrol and not diluted with alcohol.

In the US the vast majority of gasoline, regular or premium, has 10% ethanol. E85 gasoline has 85% ethanol. Only Missouri and Montana have rules that PERMIT zero ethanol. But because the refineries are all set up to produce gas with 10% ethanol, it's really rare to find 0% Ethanol gasoline in the US, even in those two states the permit 0% Ethanol. I would guess that Canada is similar. (BTW, the ethanol is not added as an octane booster, but as an oxygenated compound that reduces emissions. 10% ethanol in the gas will (generally) not damage the engine, but may damage the seals in the fuel system. Ethanol is also hygroscopistic (it attracts water) so may cause corrosion in the fuel tanks and fuel lines. Most US engines cannot handle E85 because that requires the computer to be calibrated to maintain the proper fuel/air ratio. E85 fuel won't damage a non "Flex Fuel" engine, but it will tend to run lean, which will lower fuel economy and may increase NOx emissions. Flex Fuel engines have a sensor that detects the amount of enthanol in the fuel and automatically recalibrates the computer to maintain the proper fuel-air ratio.)

KenV
14th Jan 2015, 16:13
Sorry to take this off topic slightly but when I had new tyres fitted recently the garage tried to persuade me to pay extra to have them filled with 100 % nitrogen instead of air on the basis that they would be quieter and more efficient. Given that what we breathe is 75% nitrogen anyway this sound a money-spinning racket to me. Any views ?

Nitrogen in the tires will (generally) not result in any noticeable ride difference. Oxygen is pretty reactive and removing it MAY improve tire life. However, modern rubber compounds have lots of stablizers included in them to prevent oxygen reaction. Many (most?) large aircraft require nitrogen in their tires, but they operate at MUCH higher pressures than car tires so the partial pressure of oxygen is much greater. They also operate at much higher temperatures and under that combination of circumstances nitrogen does indeed provide an advantage. There is one downside. If the maintainers/servicers are sloppy, they could mix up the tanks and accidentally put pure OXYGEN in the tires rather than pure nitrogen. The results can be spectacular.

Ancient Observer
14th Jan 2015, 17:02
My very heavily modded Elan dhc, originally a 67 model, but I got my mits on it in 73, was very grumpy if I didn't feed it 5 star 101.
Some RR engineer had spent a fortune on it......some mod cons, but mainly the money went under the bonnet. One of the OCD type engineers, special Swedish steel springs etc etc.
As I nearly killed myself in it a couple of times, it had to go. The replacement, (a saloon) though, just didn't give the thrills, so in '75 I bought a far more sedate S4 dhc. That also preferred 5 star 101, but would run on 4 star.

When SWMBO got fed up with buses, even the S4 had to go.

qwertyuiop
14th Jan 2015, 18:23
Using nitrogen in tyres is not about removing Oxygen, it's about removing water.
Race cars and aircraft use nitrogen (sometimes called dry air) in tyres in order to prevent large changes in tyre pressure.
In race cars this maintains more consistent handling and a consistent tyre pressure helps a road car tyre operate within a zone of least rolling resistance.

KenV
14th Jan 2015, 19:11
Race cars and aircraft use nitrogen (sometimes called dry air) in tyres in order to prevent large changes in tyre pressure.



In the aircraft maintenance world, there's a big difference between dry air and nitrogen. That difference is the presence of oxygen. Many aircraft maintenance manuals prohibit the use of dry air and require the use of nitrogen.

tdracer
15th Jan 2015, 02:58
I have better things to do than checking tyre pressures every week. Cooler runnng and more consistent pressure is a bonus
So, you're suggesting pure nitrogen doesn't conform to the 'ideal gas law' but air does? :=
I've had this debate numerous times with other racers - claiming that if they use pure nitrogen their tire pressure didn't change as the tire heats up. It's 100% bunk - the difference between how pure nitrogen and dry air react in a tire is unmeasureable - they both conform to the ideal gas law. The only difference is that bottled nitrogen is nearly always 'dry', while compressed air from the shop compressor usually has some water in it (especially if it's been six months since they drained the compressor tank :uhoh:). Although water vapor also conforms to the ideal gas law, if there is enough moisture and/or the temperature drops low enough, the phase change between liquid and gas will indeed play havoc with tire pressures as the tires heat up.
But the funniest part was to watch the guys that used pure nitrogen mount tires - before they set the bead they'd liberally spray soapy water all over the wheel and tire bead to lube it before inflation to help the bead seat - leaving many times as much water inside the tire as they'd get from inflating with compressed air :ugh: Have you ever watched the guys that mount your tires on the rims? Every place I've ever seen has a big bucket of soapy water that they slather all over the tire bead before inflating the tire and setting the bead :rolleyes: Oh, if you're wondering, I usually 'dry set' tire beads without any lube - if the tire was stubborn and wouldn't seat at a reasonable pressure, I had some water free stuff called "tire snot" to lube the bead.
BTW, molecular weight of Nitrogen is 28, while dry air is about 29 and Oxygen is 32. So the Nitrogen molecule is actually slightly smaller and hence more likely to leak out than that pesky Oxygen.
Pure nitrogen is specified for aircraft tires to reduce fire danger - in the event of a wheel well fire, badly overheated brakes, etc. - pure nitrogen escaping from the tires won't feed a fire, compressed air would.

DType
15th Jan 2015, 08:36
tdr
I wish you wouldn't confuse us with FACTS!

pvmw
15th Jan 2015, 09:00
I have better things to do than checking tyre pressures every weekSo you don't regularly check your tyres for any potential damage, slow leaks etc? Whatever you fill your tyres with you should be checking the pressure regularly.