[SeeSharp]

Does every (truck) diesel engine after 2010 require DEF?

Yes.

[zipper]

Thanks. I imagine older diesel RV’s could be (or maybe already are) on the chopping block too, in CA, since the diesel RV’s manufactured without DEF all precede sometime in year 2010. I don’t know if they are already outlawed. But I do know one reason older (higher-end) diesel RV’s are still popular is because they don’t have expensive DEF systems - if the DEF management computer system goes out it might be months to repair because of parts scarcity, and the system is difficult or impossible to bypass.