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PSA: That fresh engine install at PHP wasn't just my imagination
I pulled a Cessna 172 out of the hangar at Phoenix Goodyear last month that I did a major overhaul on three years ago, and the cylinder compression numbers still hold steady at 76/80 across all four. Most guys I know swear by break-in oil changes every 25 hours but I went with straight mineral oil and gentle power settings for exactly 50 hours before switching, and so far it's paid off big time. Anyone else run a long break-in cycle like that and see better long term numbers?
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lunah121mo ago
Ran the same break-in on a Franklin 6A4 a few years back... 50 hours on mineral oil before switching, kept the power between 65% and 75% the whole time and didn't let it idle for more than a minute on the ground. Compressions are still 76-78 across all six after 400 hours now. Lotta guys rush to change that oil at 25 but the rings just haven't seated yet at that point in my experience.
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moore.beth1mo ago
A 50 hour break-in seems like a lot of unnecessary worrying about something that usually sorts itself out. Most engines I've seen run fine with a standard 25 hour oil change and normal power settings. Might be overthinking a process that's been working fine for decades.
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Used to be in the same camp as you until I saw a few engines that had lazy compressions around the 400 hour mark from rushed break-ins. Going to 50 hours on mineral oil on my next one.
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