Before the switch to 20 wt oil there was a paper (pretty sure by SAE) that described shorter engine life of 20 wt as compared to 30 wt oil.
As I call the requirement was that the engine would last 200K miles. I recall that number got reduced to 150K miles. Wish I could resurect that information. It was around 2010.
As I call the requirement was that the engine would last 200K miles. I recall that number got reduced to 150K miles. Wish I could resurect that information. It was around 2010.