When my girlfriends Dad flew his plane he had 3 drums of Aircraft fuel in his hanger . My 47 and PT were using that every Sat. Nite at least 115 Octane Fun Fuel .if you have access to that highly leaded
Aviation fuel or avgas is rated somewhat different then auto fuel in that there is usually a high and low number such as 100/130. The 100 represents a lean mixture octane and the 130 is a rich mixture. This does not mean that it's octane rating is the average of the two numbers but that the fuel performs differently depending on the ratio of fuel to air. Years ago there used to be a 115/145 avgas however that was long ago, in fact I have been around aviation for about 20 years now and have never seen it. There used to be three different grades that were normally available 80, 100LL, and 100. Sometime in the late 80s early 90s this changed and 100 was phased out and 80 started to be come quite rare and only a few airports had it. Anymore 100LL is the only grade commonly available. I'm going to say that there is no way you were not running 115 octane fuel more likely 100 is the best you could have expected.
Now some of you are wondering whats the difference between 100LL and 100? Well the LL stands for low lead, lead being what they added to increase the octane rating. The interesting thing is that 100LL actually has more lead in it then the old 100. Aircraft engines (reciprocating) are pretty much old school technology in that most designs date back to the 50's and 60's. FAA certification makes it very expensive for new innovations to be introduced and most engine makers don't wish to spend the money for a market that isn't that lucrative, they also run the risk of being sued if new technology fails so they just go with what has worked and is already certified. Now the EPA of course would like all fuels to be lead free but in this case bureaucracy gets in the way because the FAA makes it almost impossible to make the changes to aircraft engines that would be needed to make them run on unleaded fuels. So avgas continues to have a pretty high level of lead.
We should all know that running leaded fuels in a car designed to run unleaded fuel is a big no no. It will mess up your catalytic converter is the big one right but what will the added lead do to our turbos? Thats a question that I can't answer. My guess is that it would not be good. I used to have access to a lot of waste avgas and would run it in my 1970's lawn mower or in a friend's boat. The reason I stopped using avgas was because the excess lead was leaving a lot of lead deposits behind like fouling the spark plugs and in the case of my mower it literally sealed off the exhaust ports. Avgas is much more highly refined then auto gas (mogas). I found that when we would run avgas in the mower or the boat a tank of fuel burns a lot faster and that is because the avgas vaporizes a lot faster then mogas. When we would run the avgas we would have to adjust the mixture on the carburetors to make the engines run smoothly. Which brings us back to are we running a rich or lean mixture and what then is the octane rating? Here is something else to consider most aircraft engines do not exceed 3000 RPM as higher RPMs would cause the prop tips to turn too fast, therefore the fuel does not have to burn as fast as fuel would need to for a higher reving engine. Who knows what having unburnt fuel exposed to your turbo would do? One more thing aircraft engines use 2 spark plugs per cylinder to help the fuel burn more throughly.
Since most cars are not set up for 100 or higher octane and the fact that the mixture is probably going to be very lean your most likely going to be getting the lower of the octane numbers along with the risk of burning up exhaust valves because the mixture is too lean. There is of course the issue of running lead in your unleaded engine oh and avgas the last time I checked was something like $6/gal, so basically what I am saying is don't use it in your car just like you shouldn't use mogas in your plane.
