Originally Posted by dublinpilot
.According to Lycoming you can't damage with leaning below 75% power.
That is, indeed, what Lycoming say.
But there's a HUGE amount of data now from GAMI's test-rig to say they're wrong - especially for the larger GA engines - and, since they've been putting out this 'advice' for so long, I guess backtracking is kinda awkward!
You pays your money, takes your choice. I fly behind a 300HP IO-550, and there is no way I would operate that anywhere approaching 75% HP with the mixture setting in Deakin's 'Red Box'.
Maybe I'm just gullible.
There again, and interestingly, TCM's advice on their engines is that you are okay operating at any mixture setting at
65% and below. That's a peculiar difference between Lycoming's advice and TCM's, don't you think, given the engines are technically near identical!