Cyclic,

Thank you for your thoughts and opinion.

As I said, the tests were done for a school assignment & also for our own personal interest, nothing more, nothing less. The objective was not to destroy an engine but to demonstrate how the general overall performance was affected by different oil % in the fuel. We mix our own fuel & had complete freedom as to the oil % in each fuel mix. The engine we chose was a 1970's OS 35 & the oil was Castrol M Castor - 2 items that are likely hard to come by for most modellers in all parts of the world & therefore, they could not perfectly duplicate our results. They would need to use their own preferred engine & fuel/setup etc & draw their own conclusions from their results.

I repeat, the tests were done by ourselves for ourselves.

The outcome of the tests showed that the manufacturer's recommended oil % was the optimum amount that gave an acceptable operating temp, good power & smooth running. This was then considered to be the baseline value & gave us the normal operating temperature for that particular engine. Too much oil and the engine was down on RPM, very smokey exhaust & low temp. Too little oil - certainly beyond the lower limits of what the manufacturer recommends - resulted in greatly elevated temps. These high temps combined with a hot summer's day (very common in my part of the world) may push the engine past the point of no return.

Armed with this knowledge about operating temps & oil % for their particular setup, the modeller can go flying at any time of the year & providing the needle valve is set correctly, correct prop size etc, no damaging engine overheating should occur.