One of the biggest causes of engine failures in engines is from insufficient lubrication. This can be caused from the result of using the incorrect oil, the incorrect amount of oil, contaminants in the oil and simple old abuse or lack of maintenance. Remember most 4 stroke oils for small engines are designed for either small commercial or industrial engines like lawn and gardening machines, pumps, mixers, compressors, generators and saws. Sure your Subaru racing engine is the same design but the one major difference is the RPM range that your engine operates at. The difference is commercial and industrial engines are governed to a rev range of around 3600 rpm and in most cases use a varied rpm operating range. The second type of 4 stroke engine oil is designed for motor cycles. Many of the motor cycle engines have an oil pump and do not rely on a splash feed and dipper style oil pick up that scoops oil up on each pass to lubricate the crankshaft/conrod. The rest of the engine, like the top end camshaft, rocker gear and internal crankshaft bearings rely on the oil being splashed around the inside of the engine. Oil choice is something that needs to be carefully considered and the oil you need is for a splash fed air cooled engine operating at high rpm for extended periods of time. We do not recommend the use of any oil additives, additives that contain Teflon, PFTE or Friction modifiers. Moly are worth a try in larger engines but when you have an engine with a capacity of around 600ml, use the best oil you can get. If you are thinking of using a full synthetic oil, use one designed for splash fed air cooled engines. Some oils we know that meet the criteria of what the requirements are for your engine are as follows:
Redline RL157 full synthetic Kart oil, Redline racing 20, Amsoil 4T synthetic kart oil, Penrite 10 tenths synthetic and oils with a high zinc content. A viscosity rating of 5w /20, 5w/ 30 is what we personally use but there have been racers using other viscosity and other brands of oil but remember, an engine that is splash feed runs a tight clearance and automotive oils that are thick like 15w/50, 20w/40 we believe are not suitable.
Oil drain time is some thing that needs consideration. An engine running at high RPM with an oil capacity of around 600 ML of oil should be changed regularly.
