Addicted Member (>300 posts)
Join Date: Oct 2018
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IMO, i'm guessing tight clearance is to even out bearing load during normal driving situations. i'm sure it has other reasons as well. we have engine turning at 8000+ rpm making 100hp/liter. it's also long and wide. every engine builder recommends higher clearance for FI and/or high rpm applications due to flex/journal deformity in those cases.
worst of all, we use 10w-60. tight clearance may be ok if the oil was thin as water, but ours stays thick. so i still don't see ANY downside to using wider clearance as long as oil pressure stays above normal for the oil we use. again, i love learning and would love to be shown otherwise.
as for piston-cylinder gap, that's completely different and not what we're talking about. not sure why that was brought up.
pav, i think it may be because the wear is uneven? oil flow may still be restricted at places where there's no bearing wear.
2006 E60 M5 with supersprint headers, mid pipe, and muffler without cat. Evolve R stage 3 tune.