Probably over my head a little then...
I do know this though, when my shop started getting into law enforcement fleet accounts the Crown Vic's were having a LOT of main bearing thrust issues on the then new 5W30 oil.
I mean like converter bolts hitting the back of the block in drive!!
Most got mains under warranty by the local Ford dealers who was using the 5W30 as it was what ford called for. They were using Valvoline.
We at the time were using Castrol. We put 10W40 in cars of any Department that would let us ( some had warranty concerns) and Castrol 5W30 in those that insisted.
We had NO main bearing failures on any car that had the Castrol, and over a few years took on most of the local agency's as word in the industry was cars we serviced didn't have engine falures like the ones being serviced at the local dealers and county garages.
So, I kind of have a soft spot for Castrol I guess...
