Reply to thread

Message: <blockquote data-quote="f8." data-source="post: 143814" data-attributes="member: 923">guys just because the 10-w60 is recommended on the m3 it doesn't mean its best on every other engine. realise that on a high revving engine main and big end clearances will tend to be on the looser side due to likelihod of crankshaft flexing.with that in mind the s54's main bearing clearance is 20-50microns which is huge considering some japanese engines have this clearance down to 4-22microns! 4 microns is 0.004mm as the space in which oil flows between the block and crank!! big clearances will require heavier oil thus w60. if the oil is too light the oil pump will have a tough time maintaining pressure with this large clearance.on the other hand normal engines with smoothness and silence and fuel economy in mind will tend to run with tighter clearances. such tight clearances will favour a lighter oil. i see no advantage going heavier than is really necessary. for sure its safer but your engine will be more sluggish and fuel economy will be down.if you notice all M engines prefer heavier oils (w60 or so) including the m5 (e39 and e90). whereas the more normal engines are recommended with lighter oils. i can almost guarantee you that the clearances on the sportier engines are on the looser side compared to your normal engines, thus dictating the use of respective oil weights.</blockquote>