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View Full Version : Premium Fuels - What is the point ?


Astrodome
4th Nov 2005, 21:21
What is your opinion of the various premium fuels (Shell Optimax, etc) that are sold at petrol stations ?

Are they worth it ?

Do they actually have a point/benefit?

Romeo Charlie
4th Nov 2005, 21:28
They do if you have a high (er) performance car.

For instance, the Volvo T5, T5R, R etc are all designed to give optimum power on 98 RON petrol due to its superior combustion qualities. If these car are run on ordinary 95 RON then 'pinging' will occur and the ECU will back off the boost thus reducing the power.

A friend of mine with a modified Volvo 740 Turbo runs 16psi boost pressure on 98, but has to drop it to 12psi when using 95. The real world (!) difference means a 14.5 second 1/4 mile at Santa Pod on 98 vs a 15.8ish on 95.

Astrodome
4th Nov 2005, 21:39
Cheers

So for an 'ordinary' car, say a 2.2 petrol Vauxhall Vectra, would there be any point in using the higher rated fuel then ?

Jerricho
4th Nov 2005, 21:50
Back in the land of Oz I had a Mitsubishi Lancer 1.8 and tried running it on Premium for a couple of weeks. I began to notice a black residue forming around the tip of the exhaust, which I could only put down to the fact that the higher octane wasn't being burnt efficiently.

As to Shell Optimax, I run my Scooby on it (gotta run it on Premium) and it may be a purely psychololgical thing but I think you can notice a difference.

Unwell_Raptor
4th Nov 2005, 22:11
When I was a boy back in the Fifties (old fart alert) TV ads tried to convince people that Esso Golden (about 99 octane) would somehow make your old banger that was okay on any petrol run better. My dad fell for it, and this weaselly and deceptive marketing is what led to the rules bringing in the star rating.

Run your car on the lowest grade fuel that the owner's handbook says is okay. All petrol of the same grade is more or less the same, and often comes from a single supply source.

Cheapest is bestest.

SyllogismCheck
4th Nov 2005, 22:19
Nearly all modern cars have a knock sensor which senses the onset of pre-ignition. At this point the ECU retards the ignition to prevent the pre-ignition. Higher octane fuels help prevent pre-igniton. Retarded ignition timing reduces power output. Ergo higher octane fuels should result in less retardation and imporove engine output. In practice only a handfull of vehicles on the road actually run that close to pre-ignition anyway, most performance turbos, Honda and BMW 100+bhp/litre normally aspirated engines and supercars.

So, no Astro, don't bother with it in everyday cars. That said, such fuels may contain superior detergent type additives which may serve to clean the injectors and combustion/valve areas slightly given a tankfull run through once in a while.
Driving your car reasonably hard from time to time will do just as good a job though.

Allegedly, a mix of premium unleaded and lead replacement petrol gives even better anti-pinking properties somehow which equates, in essence, to a higher octane rating. I'm sceptical and it's certainly NOT for cars with catalytic convertors.

ChrisVJ
4th Nov 2005, 22:33
Don'tknow about the UK but some of our fuels vary quite a lot.

Most of our suppliers, but not all, add up to 10% ethanol. Has a detrimental effect on some engines (in particular my Rotax, said to damage the seals etc and can slowly dissolve some rubber fuel line.)

Other petrols have additives that can damage engines. Locally one major gas co added an additive for a few months (without giving any notice ) that caused fuel pumps on small cars to seize or gum up. Lots of repairs paid for and additive eventually discontinued.

Mostly they all work but sometimes..........

tart1
4th Nov 2005, 22:48
I have heard that it is recommended you put a tankful of premium petrol in your car every so often to clean out your fuel tank.

Not sure who recommended that though .......... might have been a major petrol company (who of course only have the good of you and your car in their mind)!! :eek:

Kaptin M
4th Nov 2005, 22:52
I run my Scooby on it (gotta run it on Premium) and it may be a purely psychololgical thing but I think you can notice a difference.No I can't......you've never so much as even offered me a ride in it, you miserable barsteward :mad: :E

SyllogismCheck
4th Nov 2005, 22:59
Hmmmm, interesting point tart1.
I wonder if they, the fuel giants, actually worked out the most profitable formula to 'suggest'. The one where they gained the greatest improvement in sales of premium fuels without those sales actually cleaning anyones engine sufficiently to improve overall economy. :hmm:

How many litres would they lose in sales per year if every car in the country was doing an extra 2mpg I wonder.

Out Of Trim
4th Nov 2005, 23:39
Romeo Charlie

If these car are run on ordinary 95 RON then 'pinging' will occur and the ECU will back off the boost thus reducing the power.

Err that would be Pinking not Pinging! It's a sort of metallic clinking sound of pre ignition.

I occasionally run the higher octane fuel for fun.. It does make a small difference in acceleration and outright power. :cool

ShyTorque
5th Nov 2005, 00:41
"Err that would be Pinking not Pinging!"

Depends which side of the Atlantic you're referring to.

Tomato? Tomardo!
Potato? Potardo!
Pinking? Pinging!

No point using a higher octane than your engine needs. However, even if a car doesn't have an ECU, it IS sometimes possible to manually advance the ignition slightly (on some cars, not all) and enjoy slightly better performance.

I used to have a Nissan that could use unleaded OR leaded (hard valve seats but no catalytic convertor). If I was towing I used 4 star as it pinked on the standard advance setting if unleaded was used. I just used cooking unleaded around town on a retarded ignition setting, as it was cheaper to run it that way.

SuperOwl
5th Nov 2005, 00:49
I often wondered the same for a number of years but now I won't put anything else in my bike. Even though it costs quite a bit more per litre than the normal stuff, the miles/cost ratio is better than that of normal petrol. Also, the engine runs smoothly with the premium fuel than not so for me its better all round.

I can't say that I have noticed any difference in the car though.

If you only want to fill up with premium fuel to clean the fuel system, you may as well fill up on normal fuel and then add a bottle of Redex (approx 99p) and save a couple of quid.

Jerricho
5th Nov 2005, 00:52
Christ, who gave Kaptin Poopy-pants the grammar hat?

Maybe there's a reason you haven't been invited :p

Kaptin M
5th Nov 2005, 01:57
One doesn't wish to be seen frequenting with jail birds, Jerricho......jail bird Jerricho - it's got that certain ring about it, hasn't it!

I've still got my 1972 blue Toyota Corona in Briz - if you (and Binos) behave you might get a ride in her. She definitely runs better on the higher octane stuff.

sir
5th Nov 2005, 09:38
I was filling my Audi turbo at a petrol station near Zurich and the attendant came out and asked why I was putting normal unleaded in "Surely you want super in an Audi ??"

On the back of the filler cap door it specifies normal octane - might try super once though and see if I notice a difference.

fmgc
5th Nov 2005, 09:50
A mate of mine had a Triuumph TR6 (or 4 I can't quite remeber) and used to put a cap full of Avgas in the tank about every 2 weeks, he reckoned that it cleaned out the engine and carbs.

1DC
5th Nov 2005, 10:14
I use it in my 3 litre accord cos i only use the car a few times a week, less than 5000 miles per annum. I'm advised that the better detergent qualities of premium will be good for a bigger engine particularly as most of my journey's are less than 30 minutes duration..

Romeo Charlie
5th Nov 2005, 12:22
Nearly all modern cars have a knock sensor which senses the onset of pre-ignition. At this point the ECU retards the ignition to prevent the pre-ignition. Higher octane fuels help prevent pre-igniton. Retarded ignition timing reduces power output.

Indeed, I meant also to add that unless your car is mapped to run on 98, there is no gain to had by using it. ECU's will not advance timing to the point of knock/pink/ping.

Re pink/ping etc, I spend a lot of time on a predominately US based Forum where pre-ignition is always refered to as ping.
I should resist using the US word lest I incur the wrath of Herr Drapes!!

maxman
5th Nov 2005, 15:30
U_R is correct. Most fuel is made to the same spec, and comes from the same place. Take a look at all the different trucks that leave terminals.
Optimax, and the new stuff Tesco is selling seem to be the exception, 98 and 99 octane I believe.

G-CPTN
5th Nov 2005, 15:44
>used to put a cap full of Avgas in the tank

I've tried this, but it just runs out of the seams.


>I can testify to a 10% improvement in MPG between using regular 95 and 98 (in this case Optimax).
In that case using Optimax actually paid for itself.
>When I was running a Volvo S60 (Volvo recommends 98 but says 95 is acceptable). I kept very nerdy logs of fuel consumption and the difference was clear. (32 MPG rose to nearly 37 MPG)


That's logical (if 'rule of thumb').
An engine capable of running high octane fuel will generate full energy from the higher rated 'gas', whereas using the lower-rated fuel will result in less power (due to lower quality fuel AND maybe a reduction in timing advance or however the electronics compensate to avoid knock).
Strangely, Jaguar did a side-by-side comparison with a (MkII) 2.4 litre with a 3.4 litre, and achieved higher MPG with the 3.4 litre engined car (driven in the identical manner).
Not a lot of people know that.

markflyer6580
5th Nov 2005, 21:05
my 20v turbo passat with chip etc runs 235 bhp with optimax in,but detonates and runs 210 with 95 ron in it. used to run avgas in my mk1 metro turbo years ago,went like stink,no cat for the lead to damage and it helped the valve seats since you can no longer get leaded fuel.:}

patdavies
5th Nov 2005, 21:52
say a 2.2 petrol Vauxhall Vectra, would there be any point in using the higher rated fuel then ?

Personally, I wouldn't have thought it worth using any kind of fuel in a Vectra;)

Shaggy Sheep Driver
5th Nov 2005, 22:48
U_R is correct. Most fuel is made to the same spec, and comes from the same place. Take a look at all the different trucks that leave terminals.

Except some supermarket petrol. It's [email protected], and causes problems in many higher performance and not so high performance cars. And just as supermarkets selling cheap but [email protected] food have put good qualty small shops out of business (the Brits will always go for cheap over quality), same thing is happening with fuel. Filling stations closing at an unprecedented rate, so soon the only fuel in many areas will be the nasty stuff. :rolleyes:

SSD

Astrodome
5th Nov 2005, 23:01
For your information.

BSI standards for petrol (BS EN 228) and diesel (BS EN 590) have recently been updated to cover a number of changes to protect consumers, including the upper limit for blending of biodiesel with conventional diesel, the quality of the biodiesel that can be blended into diesel without invalidating vehicle warranties, standardisation of nozzle colours for petrol and diesel to reduce misfuelling, as well as more informative labelling.

Loose rivets
5th Nov 2005, 23:56
I've always wondered what you got for you money. In the sixties, I had a mini with a 13:1 compression ratio. It simply would not run on anything but five star. It did however, turn out 50 mpg at 50 mph, was equal to (the not then invented Cooper version)...and ate exhaust valves for lunch.

The question is, do you get a higher ‘cut' of fuel when you pay more? By this I mean is the vapor taken of a higher point on the stack in the refineries? Then and only then are you getting more POWER for you bucks. Anything else is just making an apparent improvement...a fix if you like.

If by paying more you are purchasing better "ignition control additive", then there is the option to work the engine harder by using higher compression ratios–or of course turbo-charging it. But surely, this must kill some of the potential?

I would like to think that it was both of the above, that would make sense...and be worth the money.

I have never understood why backing off on the timing, has the effect of stopping pre-ignition. After all, it is the ignition of gasses BEFORE the spark that is the problem...what can backing off the spark do? I am assuming that the gasses light by hot spots and compression alone. Maybe that's my mistake.

As for the source of fuel. The BMW agent in Colchester was very specific. If I fill up in supermarkets I WILL have injector problems. I never did...and never had.

In the last few weeks, I have been told here, that it was Argentinian fuel that caused all the problems in the early nineties. BMW, and I suppose Jaguar, with their magnificent V8s, ended up paying for conventional blocks to be fitted to thousands of cars. (All to do with cylinder linings ) It must have cost them meggabucks. I do know BMW blamed the fuel and that the blocks had to be changed, I'm not sure of the fuel storey.

Astrodome
6th Nov 2005, 00:14
All fuel HAS to meet British Standards.

The same lorries deliver to supermarkets as they do to all the major petrol stations...Go wait outside any petrol distribution depot !

amanoffewwords
6th Nov 2005, 00:23
My humble little 125cc Honda motorbike gets the hiccups if I put normal petrol in - only Optimax will satisfy her ;)