FlyerGirl,

to answer your question and not argue about what fuel is better. I will say this. Pattern flyers tend to be very detailed in the way we treat our equipment. Much more so than an average sport flyer. We also tend to demand very high performance out of our equipment. The stuff will work so well that we can tell right away if something is off even just a little. Namely the engines for the most part are extremely reliable.

Now I'm in AZ also and we don't get the bearing rust problems that you may find say in Florida. Namely the humidity is not our problem. Fuel used will impact bearing life and also how the motor is run. Simply putting some after run in or simply using Cool Power will not always insure no problems. Saying that Cool Power is an outstanding fuel. I switched to it many years ago and my bearing problems as well as some other little issues went away. I then was fortunate enough to develop a relationship a few years later with Cool Power as a sponsored pilot. I just want to be up front when I endorse the product so people know. I stand behind the product 100000% I run the fuel at my choice.

Next item to consider. The pattern motors we use are very high output. We use larger than normal props on them and cooling can sometimes be more of a problem for us in a pattern model. The reason is most of the engines are now enclosed. So combine high output working hard, and sometimes poor cooling compared to your typical OS46 sport engine...the result is it is harder on the bearings. Consider this the engines are putting out say 5 times the power of the OS 46 almost 3.5hp in some cases and yet the size of the engine is only about 2.5times bigger. This motor is making more power on proportionally smaller parts. Look at a 4hp Lawn Mower engine. Its huge compared to a 1.4-1.6 pattern motor.

Another contributor is where you fly. Many parts of the country fly on grass. When you do the engine especially the 2 strokes with that use carb right down low and up front will ingest dirt, grass seeds and all kinds of crap. This is hard on bearings. The 4 strokes are little better in this department as the carb intake is behind the engine, but it still gets sucked up. We in AZ fly on pavement mostly because we don't have such a thing a grass naturally in the fields and local environment....this will extend bearing life also as we don't suck up the crap.

Now all being said Bearings will wear out. They get loose in the cage that they run inside from wear. Proper oil in the fuel will help this hence the Cool Power comments from above other posters. Not all fuels are created equal. There are many good fuels out there. But there are also some that are less desirable...remember really high output, high performance motors. When they get loose this can affect the way the engine transitions and outputs its power. So its common on pattern motors to change bearings about every 300 flights or so from wear. This is typically when the ring motor start to loose their performance. The performance change is very slow over time. Pattern guys use the power and need it. We notice when it falls off. So we go in and change the piston ring. These rings are again very small for the output of the engine and the result is they will wear out before say a DA150’s rings. Most pilots will just change the bearings when they have it all taken apart because it’s a cheap (around $20) preventive thing and besides the motor is already apart.

Now most sport flyers don't get 300 flights on their OS 46 in a year. But when practicing hard its easy to get 300 flights in 2-3 months on a pattern model. Now changing the bearings doesn’t have to happen on a schedule but in most cases pattern guys will change them to save the chance of it going out and causing damage to the motor. Sometimes a bearing failure can be from wear or from rust. In both cases the failure can mean metal flakes or even the balls flow through the engine. We have expensive motors and don’t want loose metal floating around in them. A tell tail sign of a bearing issue is glow plugs going bad. The small metal flakes or rusty ones will stick to the glow plug element and the plug will go bad.

So I know this is more info than you probably wanted to know…but it gives some why’s and what for’s rather than banter about what kind of after-run or what fuel to use.

Troy Newman
Laveen, AZ