Engine Additives in Ultralights
It seems that since the very beginnings of development of the internal combustion engine people have been coming up with fuel and oil additives designed to make more power or extend the life of engines. In the early times, it was said that auto racers would put mothballs in their fuel tanks to get more power. The mothballs were supposed to dissolve in the fuel and give more punch. Since that time, other additives have been developed. Some of them were very effective, such as Tetraethyl lead, which was used up until recently when it was determined that it was poisoning the earth. Oil companies were always coming up with an exotic material. One time it was some mysterious stuff called Platformate, then it was boron. They all have mostly fallen by the wayside and now we are getting plain ol' gasoline.

In looking at the shelves of your local auto parts store, you can find a number of oil and gasoline additives. The oil additives with which I am familiar either make the engine oil have a higher viscosity or have some solvent property intended to clean up varnishes in the engine. When I purchased my first new car many years ago, the service manager tried to sell me an additive. He said that after a quart of the additive was added to the oil, they would run the engine for an hour, then drain all of the oil and drive the car 100 miles after which it would run perfectly fine.

I had just graduated from college and had studied engine design in addition to spending considerable time in the engine laboratory. I wanted to ask the critical question: Did they disassemble the engine and inspect it for wear or damage? Also, did they prepare an engineering report describing the test signed by the person in charge of the test?

I let it pass because whenever I've asked one of these suppliers of oil additives for an engineering report on tests run in a laboratory under controlled conditions, the results are disappointing.

The conclusion of all this is, don't deviate from what your engine manufacturer recommends. There is little doubt in my mind that in 4-stroke engines the new synthetic oils are superior to the basic petroleum oils. But my advice still remains, follow your engine manufacturer's recommendations. When it comes to 2-stroke oil, I am convinced synthetic oil is the only way to go. I don't believe any 2-stroke engine manufacturer recommends anything but synthetic 2-stroke oil. It burns cleaner and provides better lubrication at high temperatures and does not require a large quantity per gallon.

Oil in gasoline displaces fuel and burns slowly so it does not provide significant energy to the piston. Before the development of synthetic oils, early 2-stroke motorcycle racers would reduce the amount of oil in the gasoline and the result was more power. One regional champion told me that he ultimately went to 100:1 in his fuel-oil ratio and would win races. In the process, he sacrificed the engine but he would win races. The motorcycle manufacturer sponsored him so the ruined engine was no great loss. He would also do such things as use only one ring on each piston.

What I'm leading up to is this: Whatever you add to your gasoline it is very likely going to reduce the amount of power available to your engine's output. Yes, even alcohol reduces available power. Alcohol has a lower energy content than gasoline.

The question of fuel stabilizers comes up from time to time. For boats or power generators that sit for long periods of time between uses, the manufacturer often recommends a stabilizer. But your ultralight shouldn't have this problem. Every time I fly I usually burn more than half of the fuel in the tank so I am always adding fresh fuel. When winter comes and I quit flying, I drain the remaining fuel and put it in my old truck that doesn't require any special consideration. Of course, I do one more thing. With the fuel line disconnected I run the carburetors dry.

As a final note, if FAA hasn't approved an additive for certified aircraft, then it probably should not be considered acceptable for your ultralight.

Arnold C. Anderson has been flying ultralights since 1982, logging more than 300 hours in his Kasperwing. After 37 years in the engine and aerospace industry as a mechanical engineer, designing electro-mechanical equipment and solving reliability problems in equipment for unmanned deep space missions, Arnold is now retired. He lives in Bellevue, Washington, where he pursues his hobbies, including aerial photography and flying RC airplanes and gliders.