For those that may have a complaint about "oil" stains on their planes with heavier ratios. That happens because the oil is performing a better job of cleaning the particles out of an engine than a leaner oil mix.

For those that have the ability and inclination to remove the heads from their engines after 20 hours of running or so here's something to look for. If the piston is showing signs of "scuffing" on one side or another, the oil is not doing a good job. Those that show no signs of scuffing after 20 hours or so are doing well. My experience to date has shown no visible signs of piston wear on engines with well over 200 hours of running time using Belray products at a 50-1 mix. There are quite a few other oils that will perform just as well at reasonable mix ratios. Some engines went to over 400 hours before being removed from service, but were still running strong when they were removed.

I used to believe in a leaner mix of 80-1 and up, but no more. 70-1 is as lean as I care to go now, and that will only be on cooler days for r/c. Warmer temps will equal more oil.

Something else to consider. Warm those engines up before going out and working them hard. A cold engine gets beat up pretty quickly in the winter time!