As mentioned, reading your owner's manual is a good place to start. Keep in mind that most owner's manuals mention "normal" and "severe" duty operation of the engine. Most all RV's are considered being operated in the "severe" duty since that are almost always being operated at close to the maximum carrying capacity of the chassis. Towing is considered "severe" duty. Using the recommendations in my WH manual, my RV needs the oil changed at the 3000 mile intervals rather than the 7500 mile interval recommended for engines doing light duty.