Use of 100 low lead (AVGAS) in current Fcars

Can't be used on cars equipped with catalytic converters (without damaging the catalytic converters).

 

....And your O2 sensors.

 

Avgas is blended for big bore low rpm engines. A distillation curve and RVP not suited for automobile engines. It has additives like deicers and lead scavengers. 100LL is (Low Lead) by aviation standards but not automobile standards. It has 2 grams TEL per gallon. Avgas is around $6 a gallon. Just shop for unleaded racing gasoline instead. Be advised some race gasolines do contain ethanol.

 

don't forget about the tax man, avgas and marine fuel vendors do not pay road tax on the fuel they sell... if they sell an occasional jug of gas its not an issue, if they start selling noticable amounts, it cold get sticky about what tax may be owed... not worth their trouble and reason for their reluctance to sell it by the jug

 

According to Steve Poole, 7 years as the western states representative for 76 Race Fuel...

http://www.race-dezert.com/forum/showthread.php/44599-100ll-Avgas-Ok-to-run/page2 post# 15
"...AV Gas has a MOR (motor octane rating) of 96, R+M/2 rating of 100, and ROM(sic RON) (Research Octane Rating) of 106. ...

AV Gas is lighter than racing gasoline thus more fuel/larger jetting is required. Jetted correctly you should not experience a lean burn at WOT. ...

Av Gas is NOT designed for low RPM motors. AV Gas is designed to not detonate/preignite causing detination. This would be the same design as race fuel. If you compare the "distillation curve" of AV Gas to Race Gas, you will find they are almost identical. The "distillation curve" controls the speed of burn across the combustion chamber. ...

Remember this...OCTANE is a measure of a fuels ability to resist detonation/preignition. The higher the Octane number, the slower the fuel burns. Technically speaking 87 Octane fuel will develop more power than 118 Octane fuel. With this said, you should see gains in throttle response and HP by mixing commercial fuel and AV Gas/Race Gas. You now have some light end Hydrocarbons for throttle response and heavy hydrocarbons/TEL for detonation resistance."



Although this does not relate directly to the OP's query, because he should never run leaded fuel in a late model street car... but for those with cars that are a bit more "mature," (w/o exhaust sensors and converters) I have been running a 50/50 mix of 100LL and 93-94 octane pump fuel (which should yield ~ 100 RON) for many years, in a variety of vehicles, w/o any detectable negative effects. When being stored of the winter, I put in 100% avgas, it has a much better shelf(tank) life.

 

A couple of points:
76 Race Fuels has not made race gasoline in 10 years.
Avgas and race fuels do not have the same distillation curves.
100LL is the equivalent of 99-100 MON. http://www.bp.com/sectiongenericarticle.do?categoryId=4503701&contentId=57723 MOR and ROM as stated in your link are not ASTM terms AFAIK.
RON would be closer to 109-110. Avgas and mogas use different ASTM standards which is why Avgas uses the lean/rich number and mogas uses MON, RON, and (R+M)/2.
The "high octane" = "slowing burning" is another wives tale.

 

Bottom line is you'd be looking at many thousands to replace the cats, O2 sensors, etc.
Independent of everything else, the lead will throw a major CEL real quick.

 

I purchase 100 LL (blue) at the local airport in Watsonville, California and mixed it 50/50 with high octane pump gas. Car ran like ****.

I think that it caused an over rich fuel/air ratio since my car is already on the rich side.

It definitely will change your jetting so be prepared to change your jets.

 

Actually it should have, if anything, produced a lean condition as it generally has a lower specific gravity.

What car was this in?

 

1) "76 Race Fuels has not made race gasoline in 10 years." - Yes and ?

2) "Avgas and race fuels do not have the same distillation curves." - AFAIK, they could have the same curves, but AvGas has a tighter required specification, to ensure the prevention vapor lock, a narrower range of allowable physical properties than in automotive fuel. Generally AvGas is a higher quality fuel than pump fuel, but maybe not higher Q than some particular race fuel.

3) "100LL is the equivalent of 99-100 MON. " - Agreed

4) "MOR and ROM as stated in your link are not ASTM terms AFAIK."
MOR (Motor Octane Rating) = MON (Motor Octane Number)
ROM(sic RON) which I believe was a typo by the author and I noted it as such.

5) "Avgas and mogas use different ASTM standards" - Yes of course, as in the tighter spec for avgas, but both fuels anti-knock properties can be expressed as MON, RON, or (R+M)/2.

6) "The "high octane" = "slowing burning" is another wives tale." - Yes, more resistant to ignition under pressure and temp without spark, would be more accurate.

Regards,
Bill

 

It was in the 1975 308 GT4. It may have been lean...that is what I initially thought, but I didn't pull the plugs to inspect them.

I just thought it was rich because I dumped 20 gallons that was left in my '08 Tundra and it ran better, so I figured it was adding fuel since the modern stuff runs so lean.

 

Mixed 50/50 with pump fuel, I don't know why it would produce such a drastic change in mixture. I have been using "blends" in a range of say 30-60% avgas for many years, without any issues or need for re-jetting. Most carb tuners default a bit to the rich side, it's safer.

As I said, the only time I use straight avgas in a car or bike, is for winter storage, because the "modern" automotive fuels start turning to varnish in weeks.

Happy motoring,
Bill