Any of you engineer types out there want to weigh in on why running Mobil One 0W40 in my OM603 in Minnesota over the last 3 weeks has resulted in horrific lifter noise and wildly fluctuating oil pressure at idle. The engine is 207K old with a head job at 109K that included 12 new lifters. Previous to the Mobile one disaster, Valvoline SynPwr 5W40 in the winter and 15W40 Premium Blue in the summer at 3K intervals have been the uninterrupted oil diet for nearly 8 years and perfectly quiet valve operation. I just drained the 0W40 and replaced it with Valvoline 5W40. The lifters still sound like a thrashing machine, but seem to be quieting down, only slightly.

Any thoughts?

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Mark
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THE WHITE FLEET
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