API/CD rated engine oil is OLD. Like I think my 1977 M/B, 1978 Olds, 1979 GMC, and others I had required it. Yeah, no converters, filters or aftertreatments. The ULSD requirement is likely statutorily required, then negated by the fuel oil statement.

Red Diesel in a tractor wouldn't cause any unnecessary conversation with those who care about dyed fuel, even if you're using it to get groceries. They'd shut down every parade, if that were the case. You can get a DWI on a tractor, but they don't care what color the fuel is.