Quote:
Originally Posted by oldforder
The reason the new oil doesn't have the SM/SN rating is because they still have the high zddp content. The government doesn't want high zddp used in cars with cat. converters, because it slightly shortens the life of them.
|
You are correct. We may see the API SM or SN ratings go away on all these oils, even though there is no fundamental change to the oil itself, just to discourage use in cars/trucks with catalytic converters. I'm sure glad my Model A does not have a cat converter on it to poison!
Right now Chevron and Mobil are still showing SM or SN on their equivalent oil to Shell Rotella T 15W40. But they, too, may bow to the EPA pressure not to label it for gasoline engines. That does not mean you can't use it in a Model A.