Been using synthetic since 1996 in every engine I own, including the riding lawn mower, with no problems.
I would say the rear main issue is not specific to the oil, but that the leak was evidence of a rear main issue aside from the oil.
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2000 Explorer 4WD (wife's), 2001 Taurus SE (kid's), 2001 Ranger XLT (mine), '91 Gold Wing (mine), Stihl weedeater and blower (mine), Sears riding mower (mine). In terms of toys with an internal combustion engine, I'm winning...
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