I remember way back........someone wanted to know why big oil was not sued......think again......this tells a different story.
The oil in question is a group III.......not the true synthetic group IV/V.
The oil filter was also blamed. That's why I use only depth filters with the backing support screen,or the new Bosch Distance depth filter. In either case, a group three oil can sludge and then block the filter putting the blame on the filter when the oil was at fault all along.
This would not have happened with a 100% PAO/GROUP IV/V OIL. No sludge,and no blocked filters....period! Just a super clean engine.
This engine below wasn't so lucky with the group III oil. The opposite of super clean!!
http://www.bobistheoilguy.com/...wflat&Number=1653077
This is the very famous BG product addressing sludge issues and mentions oil quality as an issue.
http://www.bgprod.com/blendr/sludgeKills.html