View Full Version : AVGAS in Cars

Avgas man
15th Dec 2006, 09:28
Hi there, I have access to a small amount of AVGAS 100LL and was wondering if there would be any problems mixing it 50/50 with unleaded and putting it in my VW Polo Mk2 1.0 ;)


Avgas Man

15th Dec 2006, 09:42
I'm no ingineer but I can't see any problem with you doing as you describe.

Can't vouch for what might happen if you try to drive it away though.

PS didn't some bloke in Darwen get some interesting results when he fitted his car with a JATO unit?


15th Dec 2006, 09:46
AVGAS contains lead, the amount varies between the different grades.

15th Dec 2006, 09:49
Apparently the engine will start 'pinking' and making odd noises then possibly blow up (dependant on engine) if used neat.

Tis what my mechanic friend who thinks he knows everything says!

15th Dec 2006, 10:15
Hi there, I have access to a small amount of AVGAS 100LL and was wondering if there would be any problems mixing it 50/50 with unleaded and putting it in my VW Polo Mk2 1.0 ;)


Avgas Man
Why? It costs a darn sight more than good old Unleaded (unless it has come from some unscrupulous source)

15th Dec 2006, 10:16
Not sure................would it not burn the valves out???:confused:

15th Dec 2006, 10:38
'Pinking' is also known as 'knocking' or detonation -- as opposed to the desired controlled combustion -- is an early ignition of the mixture and will damage your engine as it increases cylinder pressures beyond their designed limits.

Using leaded fuel in your car will most likely make your catalytic converter ineffective as it has a higher affinity to the catalysts than the substances which they should be removing (can't remember any the compounds involved!)

In other words don't try it unless you don't want your car anymore!
And yes, how have you obtained Avgas cheaper than petrol?!

Left Coaster
15th Dec 2006, 10:39
I ran it years ago in a 6 cylinder chev malibu, but because there is a dye in the fuel, the fuel filter quickly plugged. My mechanic buddy put in a brass porous fuel filter and worked on the timing and it ran great. Wish I still had that baby...

Krystal n chips
15th Dec 2006, 10:54
The RAF used to have some sort of incomprehensible objection to the use of their AVGAS in motor vehicles as I recall-----not that I ever did of course :p

15th Dec 2006, 11:01
Yes it will screw up the cat . However it is favoured by classic racers whose engines were designed for high octane leaded fuel . We use an avgas/super unleaded mix for a classic superbike .

15th Dec 2006, 11:25
Apparently the engine will start 'pinking' and making odd noises then possibly blow up (dependant on engine) if used neat.
Tis what my mechanic friend who thinks he knows everything says!
I would question the above. In the olden days (pre electronic ignition and electronic control units) when engines had carburettors and manual/vacuum ignition timing control, the use of 100 octane / five star fuel such as AVGAS would have had little effect, beneficial or otherwise, unless the ignition timing was adjusted, in which case a SLIGHT increase in performance could be obtained. Of course, vehicles equipped with a catalytic convertor would have suffered contamination of the convertor due to the lead content of the fuel. This would be a gradual build-up over time, although even casual use would result in immediate (low-level) contamination.
Lead was included in 'olden days' fuel to coat the valve seats to protect them from erosion and burning. It is the use of 'modern' unleaded fuels in pre-unleaded fuel engines that causes burn-out of the exhaust valves. For those with 'vintage' car engines, the availability of AVGAS (used neat) would be manna from heaven, particularly if it was a high-performance 'sports car'.

Current ECU (electronic control units) engines using electronic fuel injection will detect any pre-ignition (pinking) and automatically adjust the ignition timing, so using 90RON, 95RON or 100RON (octane) fuel will be compensated-for (with an appropriate adjustment in power), so use of AVGAS will have no detrimental effect on the ENGINE.
The downside is entirely the effect of the build-up of lead in the catalytic convertor, leading to it's eventual failure (and convertors ain't cheap). This will not stop your vehicle from WORKING, but it will fail the emissions test. See above reference http://en.wikipedia.org/wiki/Catalytic_converter).

You could, of course, remove the catalytic convertor (and fit a 'through-box') whilst you enjoy the benefits of the use of AVGAS, refitting the (uncontaminated) catalytic convertor (and ceasing use of the AVGAS) prior to the emissions test (probably a part of the annual inspection test - depending on where you are domiciled).

The facts on 'pinking':- http://en.wikipedia.org/wiki/Engine_knocking

PS I have no experience of using dyed-fuel and any effect on fuel-filters.

15th Dec 2006, 12:28
Avgas Man,

G-CPTN is correct.

1. Avgas contains Tetra Ethyl Lead (TEL). The lead will rapidly poison the catalyst in the cat. converter rendering it useless. For this reason, the use of Avgas in cars in Australia is illegal.

2. Avgas has an octane rating of well over 100 RON, so you would certainly not experience detonation (knocking, pinking). Please note pre-ignition is not the same as detonation.

3. A common misconception is that Avgas will improve the performance of a standard egine. Not the case. Due to it's very high octane rating, using Avgas allows the use of high compression ratio's and/or turbo/super chargers in the engine design, thus giving higher power outputs without detonation.

4. All gasolines have dye added for identification purposes. Avgas contains no solid material that would block filters.

5. Avgas will not damage valve seats. In fact the opposite is true, the lead acts as a lubricant. Over time lead compounds will deposit on the valves and piston crown however.

6. I imagine the RAF discouraged the use of Avgas in cars to prevent excessive "stock shrinkage"!

Hope this helps

Octane (Petroleum Chemist)

15th Dec 2006, 12:49
Octane. A petro-chemist maybe, but not a mechanic for sure.
Pinking is sinonymous with pre-ignition, whereas "knock" as you rightly state is the common name for detonation. Pinking (at least as I understand it) is a timing problem, where the spark does not retard sufficiently in the cycle at low engine speeds, or advances too far at high engine speeds.
Pinking does little damage to the engine, other than reducing the efficiency as the charge is ignited too early and some of the energy produced from the expansion acts to push the cylinder the wrong way.
Knock/detonation can have disasterous effects on your average petrol engine. This is where the fuel explodes, with a flame front speed much higher than the normal ignition speed. This usually occurs due to a hot spot in the cylinder due to carbon deposits, or due to excessive compression or intake temperature. The high speed of the flame front can cause very high transient pressures and can easily damage crank shaft bearings and connecting rods (con rods). The added lead works both as a valve seat/stem lubricant and as an anti-knock additive. Modern car engines are designed to run without the lead, and use other additives to achieve the required anti detonation properties.
The diesel engine works on detonation rather than using an external ignition system, hence the extra strength required to make a diesel more reliable, but also the efficiency of a diesel engine.
The 100LL actually has very little lead in it. (the LL stands for Low Lead). This fuel has a blue dye. Fully leaded 100 avgas is dyed green. The LL contains a maximum of 0.56 grams of lead per litre. This will rather quickly destroy the catalytic effectivenes of your cars catalytic converter.
So, the answer is yes, it will run quite happil in your car, without engine damage, but it will chew your cat up and spit it out. If you can remove the cat and replace it with a straight through pipe then you'll have no problem.
I'm not sure what the legal/taxation aspects would be, and the fuel is readily identifiable as aviation fuel due to the blue dye.

<edit> Just noticed the model and mark of the car. The mark two polo was produced prior to the compulsory fitting of cat's so you'll probably not have one. I'd say you should have no problem whatsoever running this fuel neat. In fact it'll probably run better with it! You might have to get your mechanic to stick it on a timing lamp and check the ignition timing is right, but that's the work of seconds.

15th Dec 2006, 13:03
Agree with most of Octane's comments save No 4 - Motor gasoline is undyed in the UK

One point nobody's mentioned is that unless you pay the appropriate road fuel duty, those nice chaps at HMCE will impound your vehicle if they catch you (and the blue dye is a good clue := )

To summarise:

1. If your vehicle's fitted with a cat converter, it will be buggered very quickly, leading you to fail the emissions test on your next MOT
2. No performance benefits
3. Its illegal, unless you pay the duty

Matt - just seen your post, explains why chemists rather than mechanics formulate fuels :E :8

18th Jul 2008, 23:22
I have heard that Avgas 100L was used in a classic Mini in the sixties when a drum of the same was left at RAF St Mawgan by the SWEB helicopter team. I also heard that Avgas 100LL was used in a MGB GT in the seventies both pre cats. Both occurrences caused no problems whatsoever but the fuel was introduced into half full fuel tanks.

19th Jul 2008, 00:22
Used to run a hot Chevy 350 V8 on Avgas as it didnt run well on regular pump fuel due to the high compression ratio of the engine.

Ran very well with plenty HP sauce!

Desert Dingo
19th Jul 2008, 00:46
The lead in avgas will kill the exhaust gas oxygen sensors fitted to modern engines.

19th Jul 2008, 00:46
in the 60's ran various side valve V8 Fords on avgas .Austin A40,MK1 & 2 Zephyr,Velox,R Model Bedford truck etc
You could always tell a cropdusters car in a car park..it was the one that weathercocked into wind and smelt funny when running..:rolleyes:

Black Box Barney
19th Jul 2008, 00:53
I've been running various petrol engines on it for years, still am, but NOT WITH CATS.

Never had a problem yet.
Blew a head gasket on a 2.0 DOHC Granada a few years back (nothing to do with the Avgas) and expected to see the worst once I whipped the head off, what with all the rumours and stories . . . .

It was a clean as a whistle :ok:

I'm currently running a 2.9 V6 Granada on it, still no problems in over a year.

The only thing I have noticed is, all the exhausts on the cars were white inside the tail pipe, not black, don't ask me why, I haven't a clue !!

19th Jul 2008, 01:55
I agree with Octanes comments.

I run a cocktail of 25% Avgas 100 LL ( legally obtained !) in my ancient VW Beetle 1200 cc engine fitted to a Turbulent Microlight aircraft. I'm a pilot, not an engineer, just want to fly the bloody thing not worry about what makes it go, but the local NZ pundits reckon that the 25% ratio effectively makes the now non-leaded motor fuel equal to the traditonal stuff no longer obtainable.

The Aero Club Rotax equipped microlight is certified for both, but if we use Avgas then the oil starts to look like yoghurt after a few hours - not nice, tho apparently it doesn't matter, it's just the lead, but we have to change the oil / filter / plugs every 25 hrs. v. 50 hrs with petrol.

The local Petrol-Heads with old Stock Car Racing bangers are always trying to get their hands on our Avgas, as they reckon their 50's style engines need the lead.

Aside - both Diesel and Avgas are cheaper than the cheapest ( 91 grade ) motor fuel in NZ, but I'm not an Economist, either !

Charlie Foxtrot India
19th Jul 2008, 02:03
If we have Avgas that's been drained from an aircraft and can't go back in unless strained through a chammy, (a very very slow process) I put it in the MGB and it runs as sweet as ever. No problems, no difference in performance, just smells a bit funny, wonder if Plod knows the difference?

19th Jul 2008, 02:31
Oh..thats right ran a Landcrab onnit for while no probs..well until it died from suspension failure.:uhoh:

19th Jul 2008, 03:06
Drove a '76 Le Car home from the dealership, read the manual and found it required premium leaded fuel.

The noted with dismay that the premium pumps were being displaced by unleaded pumps:uhoh: Tried premium unleaded and got knocking:ouch:

So developed the habit of stopping by airports and filling up with 100, not 100LL.

The car loved 100.

Also would fill up an Explosafe gas can. Would drive down to half a tank and fuel with unleaded. Then drive to empty; pour in 100 from can and fill with unleaded. Smaller airports would generally sell to me, but over the years more and more had to turn me down as the plod turned the screws on them.

Then one day, found myself with no 100 whatsover near a gas station without premium unleaded; so, tried regular leaded.

Car was perfectly happy:ok:

Engine ran just fine with 100, but found that CV joints were only good for 25,000 miles and that after replacing several mechanical bits, found that the rust mites were no longer holding hands past 110,000 miles.

Later moved into a duplex where the landlady drove an R5. Firmly told her to get rid of the car before 70,000 miles.

19th Jul 2008, 10:25
AVGAS 100LL does still contain a high content of lead when compared to old fashioned 4 Star motor fuel. The "low lead" suffix refers only to how much AVGAS used to contain.

4 Star contained a minimum of 0.05 gm/ltr of lead.

AVGAS 100LL contains up to 0.56 gm/ltr of lead. Note this is 11 times as much.

AVGAS 130/100 used to contain up to 1.28 gm/ltr of lead, or 25 times as much.

Therefore, a gallon of AVGAS 100LL in a ten gallon tank of premium unleaded would appear to have about the same lead content as the old 98 octane rated 4 star. The resulting fuel quality (octane number) might be better than 98 because the base stock is better.

Again, DON'T put leaded fuel through a catalytic convertor, the lead halide salts produced by combustion will coat the platinum matrix and render it useless very quickly.

19th Jul 2008, 10:44
Years ago, a work colleague who knew I was a pilot asked me if I could obtain a sample of Avgas for him. He was into hillclimbs. Apparently some of the competitors has suspicious performance advantages and Avgas was suspected. So he needed a control sample to catch the miscreants. The blue colour being the giveaway. A lot of older cars run well on it.

19th Jul 2008, 11:13
So he needed a control sample to catch the miscreants.

And using this "control sample", did he manage to catch them, or even beat their hillclimb times? ;)

My older technology competition car likes AVGAS in small doses, used when off-road only, of course.

Metro man
19th Jul 2008, 11:41
Customs may object to you using AVGAS in a road vehicle. If you use untaxed RED diesel (agricultural/construction use) in your car they can sieze it. They can also assume that you have run the car on it since new and charge you duty on the fuel you would have used to cover the cars total mileage.

21st Jul 2008, 20:07
Put it in a Lada Samara and it rotted the the fuel pump diaphragm!

Also Avgas seems a very agressive degreasant.
Could it quickly wear out small bore engines?

21st Jul 2008, 23:10
Knock sensors in most cars work the opposite way around to the way a previous poster explained. The car is designed to run on standard pump fuel in the market county and if you use a lower octane fuel the sensor will retard the ignition untill the detonation stops. They are not normally able to advance the ignition beyond the factory setting.

Pugilistic Animus
21st Jul 2008, 23:42
No knock damage would occur just the poisoning of the CC mentioned previously--AVGAS has 100 octane

octane is correlated to antiknock characteristics as follows
pure straight chained octane has poor pre-ignition characteristics as determined by a standard reference cylinder, of n-Octane[0 octane] and it isomer 2,2,4- trimethyl pentane [100 octane]---the ratio of these two components is the octane number==example a mixture composed of 98% 2,2,4 - trimethyl pentane and 2% n-octane would be 98 octane {gasoleen}:}
so 100LL is actually almost pure 2,2,4 C5H8(CH3)3--in terms of antiknock characteristics---very important in low RPM high compression engines;)

forgive my chemical formulae it's been a long time since organic chem--back when I was an overly ambitious triple major student--so--IUPAC an I are not quite on speaking terms anymore:8


Atlas Shrugged
22nd Jul 2008, 02:23
MK1 & 2 Zephyr

Bloody hell, now that was some car.................:ok::ok:


22nd Jul 2008, 09:49
None were caught, shy torque. It wasn't really intended that anyone would be caught. The inspections were well telegraphed. Thus no one had any trace of the offending blue avgas in their tanks at the next meet. It was after all, a club meet rather than an international championship.

22nd Jul 2008, 11:06

Thanks, but when I said "caught", I actually wondered if it improved his own hillclimb time, if you know what I mean ;)

22nd Jul 2008, 11:29
Back in the good old days (60s) on certain coastal stations engine fitters carried two toolbags, one for tools and one containing an empty, one gallon can. T'was the work of a minute to fill it from the little drain trap in the wheelbay.
Periodic vehical checks exiting past the guardroom were rarely successful but mention was made sometimes of plug problems.


22nd Jul 2008, 13:15
I liked the Mk3 Zephyr that I ran for several years. Can't say the same for the Mk4 though.

22nd Jul 2008, 14:13
Thanks, but when I said "caught", I actually wondered if it improved his own hillclimb time, if you know what I mean

Aha! No, I just gave him enough to fill a sample bottle. He wouldn't have got very far on that. But if he wanted more Avgas, he only needed to ask:E

26th Apr 2009, 07:21
This is absolutely correct (Quote from DucatiST4) ....."Knock sensors in most cars work the opposite way around to the way a previous poster explained.
The car is designed to run on standard pump fuel in the market country and if you use a lower octane fuel the sensor will retard the ignition until the detonation stops. They are not normally able to advance the ignition beyond the factory setting."

High Octane fuel doesn't blow engines up as someone mentioned. It doesn't make any more power either. There is absolutely no benefit to filling up with High Octane fuel. Though if it contains lead (TEL) then it will in a short time, kill both the O2 sensors and the cats. Also if the car is running full closed-loop it will develop starting and idling problems.

If a car is open-loop then the cats and O2 sensors should be removed before running leaded fuel and the ignition should be advanced to take any advantage of the increased anti-detonation properties. Only then would there be any benefit.
Going from 98UL (RON) 92 MON+RON/2) to something like 100LL would allow an approximate 8-10% increase in power if both static CR and ignition advance were adjusted accordingly. It doesn't need any additives it can be run as is without any mixing of any sort. I've never heard of it fouling plugs either.


blue up
26th Apr 2009, 07:42
Check your fuel lines, guys. In the UK we have ethanol added to our fuel ( for the last year or so) and it has a nasty habit of eating rubber fuel lines and pump diaphragms. I had a Morris that sprayed fuel over he exhaust after the N.O.S. (new old stock) hose reacted to the ethanol and turned rapidly brittle before shattering under vibration. There is a 'mandatoty' in the PFA world for fuel line inspections. Surely someone elsehere can elaborate on this. I changed all of my hoses to BING see-through lines which are ethanol proof but there is still some concern about the long term affect on Carb bodies and seals.

I worked on light aircraft for 6 years before going straight and we used salvaged avgas to power everything.

26th Apr 2009, 08:03
While in uniform I and several friends ran cars on this .I myself had a 1955 Rover 75 which ran very well on it.Friends with Minis would mix it with regular fuel,I did this for @3 years with no ill effects to the engine apart from a green stain on the carbs which I would clean each week!Sometimes the SIB people(special investigation branch)would set a road block at the guardroom and dip tanks but our security system always let us know when this was on so the alternative route was used(other side of airfield over the railway line!!)Petrol at that time was @26p a gallon!

26th Apr 2009, 08:55
Sneaky nostalgia pic.


26th Apr 2009, 12:42
The only thing I have noticed is, all the exhausts on the cars were white inside the tail pipe, not black, don't ask me why, I haven't a clue !!
That's probably white lead carbonate, the same stuff that used to be the major component of white paint, though it's banned now. You really do not want to ingest any of that stuff... :ooh:

unstable load
26th Apr 2009, 12:44
I ran my 1275 Mini on 110 and 100LL when it came out with no hassles and later my V8 Rover with same results.
According to a chemist at the local refinery the fuel is better for upper cylinder lubrication due to the higher content of TEL and as long as the engine is in good condition and runs at 10:1 or higher compression ratio you should get a slight improvement without any modification aside from timing being accurately set-up.
My Moto Guzzi doesn't like it for some reason, though.:{

26th Apr 2009, 19:22
I've never heard of it fouling plugs either.

But the possibility of plug fouling is one very good reason why aircraft power checks are done just prior to takeoff......

My old BSA 250 which needed to use 5 star due to some fairly extreme engine mods and cold grade spark plug used to need the lead salts removing from the plug and the back of the exhaust valve on a fairly regular basis. Modern unleaded motor fuels run cleaner in this respect.

26th Apr 2009, 19:39
I had a 2 litre Lancia (Fiat 2OHC). I warmed it up with a cam, carbs, flat top pistons etc. Miscalculated compression ratio and ended up with about 10:1.

A thick head gasket wasn't an option, so I ran the car on green BP100, ie 100 octane. It wasn't avgas, but was close and cost more than super. I had to use it to prevent pre-ignition and ran the car with the ignition adjusted as far as it would go.

A previous poster is right. I didn't beef up the main bearings and after about 10,000 very quick kilometres I blew a main bearing.

So my experience: using high octane prevented pre-ignition in an engine with a high CR, but didn't take long to blow the thing apart. Even if I'd strapped the main bearings, I think something else would have given way. In other words, I'd stressed the engine in excess of its designed margins. Trust the engineers.

27th Apr 2009, 12:14
A guy called "Knocker" West had an M-type Jaguar.
With specially fitted 120 gallon fuel tank.
Went really well on the "Fuel drain" surplus from "Connies".
The car was green so you never noticed.

29th May 2012, 18:02
For info the 100 in 100LL Avgas is not the RON or Research Octane Number referred to (normally) by garages for road Fuel is the MON or Motor Octane Number which is always lower than the equivalent RON.

From Memory 100LL is termed sometimes as 100/120 because with the Tetra Ethyl Lead the MON is 100 and the RON is 120.

Its also now possible to get unleaded Avgas known normally as UL91 this recent version of Avgas is becoming more popular as Rotax engines increasingly in use in LAA aircraft and some type certified aircraft don't get on well with 100LL with the oil having to be changed at twice the frequency when run on 100LL and the cylinders are known to build up deposits with 100LL so UL91 gives owners the tight quality controll and storage tracability of Avgas without the Lead.

Again the number is the MON not the more common (for road fuels) RON and the equivalent RON is 96 meaning its just into super unleaded RON rather than the 95 RON of normal unleaded.

Needless to say while UL91 would not poison any cars cat and would run in pretty much any car there would be no performance difference at all.

I know a local guy that races scooters (yep there are people who race anything!) He uses Avgas (100LL) from the gliding club as with the approriate timing adjustments the additional octane = more power.
Needless to say he doesn't run a CAT.

I also know some years ago a Rally co-driver who ran a team for several years. Back then (early 90's) the rally organisers of major rallies used to provide Avgas (100LL) to fuel the rally cars that mostly were tuned for this fuel. Needless to say modern WRC regs don't allow leaded fuels.
He actually ran a team rallying Honda's and sadly the engine was only rated use unleaded and 100LL would have caused problems (similar to the Rotax). He came back from one rally and gave me vouchers for 1500 litres of free Avgas, only problem was they were from Air BP in Cyprus :{


29th May 2012, 23:50
From Memory 100LL is termed sometimes as 100/120 because with the Tetra Ethyl Lead the MON is 100 and the RON is 120.

My memory tells me that the 120 actually means the equivalent rating on a richened mixture for use in supercharged engines.

Edit: Ah yes, it's mentioned in this article from Shell:

AVGAS Facts and Future | Shell Aviation (http://www.shell.com/home/content/aviation/aeroshell/technical_talk/techart12_30071515.html)

30th May 2012, 01:19
100/130 actually.

100 = minimum 100 MON (lean rating tested on a MON engine)
130 = minimum 130 Performance Number (rich rating tested on a Supercharge engine)

30th May 2012, 02:52
In the days before catalytic converters I ran various VW Beetles for years on 80/87 avgas and Aeroshell 80W oil.

Pinky the pilot
30th May 2012, 03:19
I ran my old TA-22 (1974) Toyota Celica on 100LL for several years with no problems. The engine was a worked 1600 Twin Cam with a fairly high compression and 'three quarter' race cams. (Little power until revs got to around 4,000, then :eek:)

Car now sitting at back of local crash repairers pending full restoration. And fitting of Fuel injected Turbo engine.:E

Loose rivets
30th May 2012, 06:06
I had an early Mini and the head was shaved so far we had to braze a length of brake pipe into the port we'd cut into. It measured at >13:1 compression ratio.

It was quicker to c 40 than my 3.4 MkII and regularly cruised at 50, giving 50 mpg. (on the 103 miles from the coast to LHR)

The problem was, it would only run on 5 star. "Shell, with ICA." the ads would proclaim. Ignition Control Additive I think. I have a vague memory of 105. Wazzat about?

The other problem was a maximum valve life of c10,000 miles. Never seemed to burn the seats.

To stop the engine twisting, an anti-torque rod had to be fitted, and I've just had a flashback of drilling an old penny as a washer to keep it on. Funny the things one remembers.

Just can't think why 'we' didn't go for the lean burn technology.

I used to tune all my cars to give a tad of white on the plugs and in the pipes. That was a good compromise.

30th May 2012, 06:07
in UK there was a petrol shortage, and owners of cars were issued with vouchers.

I was based in Bristol, and flew single pistons.

I always did a full and complete fuel contamination check, every day or was it night...........
The residual, being a green chap, was poured away into a triumph herald bowser......

Being leaded and a no cat type engine it was very happy, thank you.

Not certain if I would be so keen to do a fuel drain on my current toy....

However my Russian friends never run short of heating oil, or truck fuel.

Loose rivets
30th May 2012, 06:43
Very tempting to run a car on heating oil. I used to pay 35 for 500 gals of the stuff. And I got Green Shield stamps.

Out in the sticks, there's no shortage of farm diesel. There was also a very fine small run of BMW 7 series that was so rare it would not attract attention. Never seen one before or since. Incredibly quiet. Stood there thinking about it, but just couldn't cross over to the dark side.

Good job really. It seems HM Customs know all about hidden fuel tanks and switchover pumps.

30th May 2012, 09:39
Not really AVGAS in cars, but..............heard of two guys selling an old petrol Mercedes. The ends/mains had gone and they couldn't be bothered with the old Kit Kat wrapper trick.
So they splashed a bit of diesel around the filler cap, stuck a "D" on the back, and sold it - quickly - at a premium.
Sort of, "what steps did you take?" - "Bloody great long ones!"

30th May 2012, 11:06
I'm puzzled as to why anyone would want to put Avgas in a car. Surely you'd get better value out of it by flogging it down at the local flying club?

30th May 2012, 11:40
I (from a LAME) the flame front is slower in 100LL (compared to unleaded), leading to a negative effect (on the valves?) when used in automotive applications.

Milo Minderbinder
30th May 2012, 12:08
Early Hillman Imps would like it. They had 10:1 high compression engines designed to run on 100 octane / 5 star.

30th May 2012, 13:12
Pre-ignition tends to burn a hole in the centre of the piston, detonation destroys the edge of the piston crown.

After an excellent landing etc...

30th May 2012, 13:17
"One careful owner"

Careful not to spend any money on it.

31st May 2012, 15:16
Early Hillman Imps would like it. They had 10:1 high compression engines designed to run on 100 octane / 5 star.

My modified 850 engine likes it too, only twelve to one since we reduced the CR a bit. A gallon of the stuff in a full tank of unleaded gives about the same lead content as the old 4 star did.

It's obvious when it's been run on a little AVGAS, it leaves a whitish grey deposit in the exhaust, just like in the old days..

Beaver man
2nd Jun 2012, 13:46
It's amazing how diligently I used to carry out the water sediment check on the beavers, (DHC 2s!!), just as my leave was getting close!! 5 gallons a time...just to be sure! Never did my old mini clubman any harm! Just had to add some OM15, (H515) every so often. But that was before unleaded.

A Squared
6th Jun 2012, 20:15
The ends/mains had gone and they couldn't be bothered with the old Kit Kat wrapper trick.

Kit Kat wrapper trick? :confused:

6th Jun 2012, 20:25
The ends/mains had gone and they couldn't be bothered with the old Kit Kat wrapper trick.

Kit Kat wrapper trick?

Kit Kat is wrapped in (aluminium?) foil - ideal for shimming-out bearings.

Loose rivets
6th Jun 2012, 20:36
Some of the early wheeler-dealers could be found on spare lots on the London side of Colchester. One guy spent the day under a big old car with a dog lead and grinding paste, taking the ovality out of the big ends.

He said something like, 'If I make fifty quid on this, it's worth a days stropping.'

EDIT: (There, beat them to it.)

A skipper checking me out on DC3s, when telling him this tale said, 'Yes, there was a lot of ovality about after the war.'

Made me giggle, that did.


7th Jun 2012, 11:02
As fire officer at Seletar in 1967 I used to be given 45 gallon drums of time-expired Avgas for use in practice fires. Not a drop ever found its way into the tank of my 1959 Zephyr.

Honest ;)