Originally Posted By: mbacfp
Should I continue to stock up on CJ-4 oils? Didn't have a diesel when CJ-4 came out, so not sure of any learning curves in the oil technology?
I joke about it, but I'd say no. The oil companies aren't going to give away a pile of sales on vehicles that use CJ-4 or older on the upside of selling oil for vehicles that do not yet exist. Backwards compatibility has been the cornerstone of API service categories, and will remain so. There will be part of the specification that won't be backwards compatible, but the other part will be.
The high HTHS component of the PC-11 specification will be backwards compatible, as always, and perfectly serviceable for earlier categories. Of course, there will always be people worried that the older was better, but that doesn't tend to actually manifest itself in the end.