I don't try to second guess service intervals. I'm not smarter than the engineers that wrote them. Most are both time and mileage based for a reason. For example, air filter paper elements degrade with time due to adhesive degradation, regardless of use. If I were purchasing a used RV and saw someone skimping on maintenance because they weren't using the rig enough that would be a huge red flag.
Air filters have a 2 year interval. For the most part my maintenance intervals far exceed the mfgr recommendations. However I have a very high level of experience with heavy duty vehicle maintenance, not the least of which has been with emergency vehicles, and I am able to weave a little common sense in with the check box method. Hence my answer to what I consider a legitimate question.
Minor edit added:
As for the engineers, all the maintenance intervals are a result predictions and assumptions based on over the road trucking. A good example is the DEF filter. The recommendation is anywhere from 150k miles to 300k. Thats fine for a trucker that drives almost every day and burns up 150k miles or more each year. But the way we operate our coaches, we need to make that an annual maintenance item regardless of milage. And on oil, while they say 15,000 miles between oil changes, for a hard working little 6.7, I would never run one that long without an oil change. I can see 10k for an 8.9 but that’s about it.
As far as I’m concerned, these engines operate under severe duty conditions hence my oil change interval of 7,500 miles, at the most. Sometimes it was closer to 5k if my next trip would pass 7500 while I’m on the road. Oil is cheap and engines aren’t and I’d rather do my oil changes at home, than in some parking lot. I’ve done that more than a few times but I prefer not to.
The point is that my maintenance ethic is more conservative than the mfgr’s and from that position I can easily provide the advice in post #3. I used to go round and round with the guys at the city garage trying to get them to reduce intervals on fire engines and ladder trucks because we used them very differently than garbage trucks or city busses.
So that’s where I’m coming from. The book is a good guide and starting point, but sometimes the coach don’t read the book.
