Make your engine last longer with additives! Increase your mileage 50%!

I’ve received a number of comments concerning the use of additives in the fuel or oil of aircraft. They range from “”I’ve seen #2 diesel fuel gel at cold temperatures even with an additive”” to “”I’ve added such and such an additive to my oil and now I get over 50% better mileage and my engine will last forever.””

I’ve received a number of comments concerning the use of additives in the fuel or oil of aircraft. They range from “”I’ve seen #2 diesel fuel gel at cold temperatures even with an additive”” to “”I’ve added such and such an additive to my oil and now I get over 50% better mileage and my engine will last forever.””

We can group additives into three categories: recommended additives; additives that sound great, but do absolutely nothing but cost you money; and additives that may not be recommended, but do actually work.

The first category is a small one. The only additive currently recommended by an engine manufacturer is the Lycoming LW 16702 additive. It helps improve cam and lifter life and is contained in several currently marketed oils. I guess we could also add the Alcor TCP additive to the list as it is approved for use as a spark plug anti-foulant in basically all piston engine aircraft.

The second category is probably the most interesting. I cannot tell you the number of times people have talked to me about a new additive that they found and the wonderful things it did for their engines. As part of my job at Shell, I evaluated a number of these additives in carefully controlled tests and found that none of the ones tested had any significant improvement in fuel economy, increasing power output or extending engine life. However, most of them had some negative effect, usually on long-term engine life. For example, when I tested some of the Teflon additives, there was no immediate benefit. Part of the reason was that the oil filter had removed almost all of the Teflon in the first pass, which put the filter into bypass mode. This reduced filtration of the oil would have a negative effect on long-term engine life if the additive were used at each oil change.

The most confusing part of this is why people believe that an additive works because a friend of a friend’s cousin’s brother-in-law’s shop teacher claims that he saw it work, but will not believe hard statistically significant test data showing otherwise.

It reminds me of the story about a guy whose car got super great mileage, but when the factory found out about it, officials exchanged his carburetor for another one that got much poorer mileage. Supposedly, the first carburetor was an experimental model that was accidentally put on at the factory.

I know we all wish there was a magical additive that would fix our broken engine and make it run as good as new. But there isn’t. If you hear claims that sound too good to be true, they probably are.

In the aviation industry, a great deal of time and money is spent trying to ensure that the products you buy and use will work well in all types of service and under all types of conditions. If an additive actually improved your mileage by 10% and caused no problems, every oil manufacturer would have it in their oil by sundown tomorrow. And if an additive actually extended the life of an engine with no negative side effects, engine manufacturers would be calling for it in a service bulletin. The bottom line is there are no magic potions. The only real magic is proper operation and service of your aircraft. So instead of looking for the perfect additive, change your oil more often. It will save you money in the long run.

What about that third category of additives that work, but are not recommended? The closest we come to having an additive in this category is Marvel Mystery Oil.

I have seen no data that show any significant advantage for this additive. But a number of pilots claim that it has reduced their intake valve sticking problems, so I will give it a marginal pass. However, I still think that this category is just a myth designed to keep cock-eyed optimists in aviation and to give columnists something to write about.

Ben Visser is an aviation fuels and lubricants expert who spent 33 years with Shell Oil. He has been a private pilot since 1985. You can contact him at [email protected].