Conversions to Unleaded Gas or Diesel Fuel
Anyone fly a plane that uses Unleaded Gas or Diesel? Doese it save money? How do you like it?
Lots of planes have STCs available to run car gas. That's about as contentious an issue as there is in aviation. Stop by Merril Field at Alaskan Aircraft Engines and look at their display case of removede parts. I've burned car gas when I needed to, but I usually use 100LL avgas.
Diesel? I think you're using slang for Jet-A. These engines are relatively new to the market and are horribly expensive. The last time I looked a 180 engine conversion was over $80K. No thanks. I don't know or know of a single person who's converted to a Jet-A piston engine.
There are new engines that run on Jet-A and diesel. They are rare though.
I burned mogas in my O-320-E2D for a couple hundred hours. Repairing the engine cost me more than one hundred times what I saved buying the less expensive fuel. I can't say for sure that the auto fuel was the cause of my engine damage but the mechanics were all in agreement that it was a contributing factor.
It's fun to listen to all the arguments for and against burning unleaded auto gas. Everybody has an opinion. In the end, it is a personal choice and everything in aviation involves compromise. Remember that the older model low-compression engines weren't designed to burn 100LL either.
I would be interested in one of the Jet-A conversions that are now approved for my airframe but the **** things must be constructed of platinum if the price of conversion means anything.
When you ran MOGAS did you mix it with 100LL or just run strait MOGAS? I have heard mention a few times that the 100LL has a certain amount of lead in it that acts a lubricant. Anyone have any feedback?
I probably mixed it some. For example, on a cross country flight to a distant airstrip I always fueled with 100LL to continue or before returning to base. For local flying, I always refuled at the mogas pump we had on the field. Most of my flying is cross country but I have long-range tanks and could usually make it home before having to fill up with the more expensive fuel.
I have heard that some guys mix mogas and 100LL at varying ratios (1 : 1, 2 : 1, 3 : 1, etc. depending on whom you listen to) but that practice is unrealistic unless you confine your flying to short hops and always return to home base to refuel.
I don't mean to discourage those who wish to burn auto fuel. If you read all the data from EAA you will see that they have some caveats about its use but they mostly endorse it for those engines and airframes for which it is authorized. I may have simply had some bad luck.
The question always arises whether I would use auto gas in a pinch. The answer is always yes. I won't hesitate to use it to get back home. But, I will never again use it as primary fuel in my aircraft (1968 C172I). As they say: other's mileage may vary...
One of my problems is that I am not mechanically inclined. I fully understand how the human body works but I can't/won't work on my own aircraft engine. That is anamalous for an Alaskan pilot. Most aircraft owners I know serve as their own A&P.
Here is some info on Auto gas STC
Lead in fuel serves as a lubricant, raises the octane rating and serves as a cushion for the valve/seat interface. Most STC’s for use of auto gas (mogas) in a certificated engine exclude the use of auto gas during the run-in and break-in process.
Until January 1986, regular auto fuel contained a maximum of 1 gram of lead per gallon. It now contains a maximum of 0.1 of a gram per gallon. No minimums were established under the new lead content regulations so it is possible to obtain regular with the same lead content as unleaded, or .001 of a gram per gallon.
It is recommend that you use one tank full of 100LL every 75 hours to replace lead on the valve seats, unless hardened valves and seats are installed. Same thing had to be done to muscle cars or the use of lead additives. Lead builds up on these parts and will not be "washed off" the first time you use an unleaded fuel. By using 100LL only every 75 hours, you will be supplying adequate lead for these parts. Also, during break-in following an overhaul or replacement of a cylinder, you should use 100LL for 25 hours in order to supply lead during the break-in process. A mixture of 75% unleaded and 25% 100LL yields a lead content equivalent to 80/87 octane avgas (0.5 gram per gallon).
Burning an occasional tank of 100LL should not be necessary if the valve's, guides and seats were constructed in accordance with the latest specifications. In view of the fact that 100LL is eventually slated to be replaced with an unleaded high octane fuel, anyone facing an engine overhaul would be well advised to seek out hardened, newer spec parts.
Parts of this is borrowed, cause im not an engineer
I think it would be cool to make planes that run on E85.
So you can run regular auto fuel w/ out any mods if you needed?
You can run regular gas in SOME engines. the 150 hp Lycoming for instance. Ive run close to 100% car gas in my cub for over 30 years and never had a problem. All have gone to 2000 hrs or well over...lets see, thats 5 engines so far. On the last rebuild, done at full TBO, (the third on this engine by the way) BJ's in Palmer said it was the best looking core they had ever seen, still looked like new aluminum throughout and all still standard bearings. That cub has not seen a dozen tanks of 100LL in the last 6000 hours... so dont tell me that it tears engines up.
I know I know, car gas was not legal back in the '70s. Well, we ran it anyway in the bush. 100LL 80/87 and all that was not, and is not, available in many a village... mo gas is always available. Car gas gives a lot fewer foul plugs then does 100LL unless you run platinum plugs and the thin wire plugs are just better all the way around...except for expense. 85 octain is higher then the 80 octain minimum required in engines made to run 80/87 for gosh sakes. Before they stopped making 80/87 all the FAA papers said it had problems with vapor lock. All those hypothetical problem just went away from FAA literature once the STC came out for car gas and there was no more red gas. Go figure. I use my cub every day up to 9,000 and occasionally over 14,000 and never had a problem.
And yes, there are no mods. Just an STC and a clamp ring around a valve tube thats supposed to show its been STC'd. I dont know of anyone that still has that silly ring still on their aircraft. You do put a placard around your gas cap saying its OK to use car gas.
Last edited by supercub driver; 04-29-2007 at 18:44.
Reason: one more thought