Nah, no 20W-60's, 70's or the like. There was the study posted a while back on HTHS and the requirement to stay above 2.6. We are all pretty confident (even us Aussies are starting to turn around on the issue) that a 30 weight will not destroy an engine (in spite of Shell XMO 15W-30 - must have been near 100 V.I being labelled as such 15 years ago). I was looking in the diesel oil analysis section at the viscoscity drop apparently associated with around 5% fuel dilution. The resultant viscoscity was within my manufacturer's range of acceptable, but most certainly would not have been if I'd started at 10cst. Is potential fuel dilution a genuine reson for picking a slightly thicker oil ? Sort of like an insurance policy for an undiagnosed injector problem ?