In the "for what it's worth" category a very
experienced engine rebuilder told me some years back that he had seen a change
in cylinder wear patterns over the last few decades. In his opinion using
the accepted leaning technique of the 60's and early 70's, i.e.
50 degrees ROP, was resulting in more and earlier cylinder wear when that
technique was used in the 90's. He said that now (which was about 10 years
ago) it was necessary to run closer to 150 degrees ROP when running 70 - 75%
power. (Running LOP wasn't common at this time.) His hypothesis was
that this was the result of changes in our fuels. I have seen no data to
support or refute this hypothesis, but it can make for some interesting hangar
discussions the next time you're hanging out at the airport and weather is below
minimums.
Tom Gourley
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