There’s a lot of arguments concerning gas v diesel. I went with gas strictly from an economic standpoint and even with the poor fuel mileage it works for me. One guy, who was a retired diesel engine mechanic, went with gas simply because he knew that cost for diesel engine parts could be budget busting. On my RV, a 1994 33’ Class A Holiday Rambler, the 460 V8 developed a bearing knock at about 60,000 miles. However, I don’t blame the engine but rather the previous owner’s irresponsible attitude when it came to regular service and maintenance. I fully expect to get +100,000 miles from the rebuilt long block engine assembly I installed. But, unlike the RV’s previous owner I’ll be running synthetic oil exclusively and changing it on a yearly basis.
Based on my own experience, I strongly recommend that whether you go with gas or diesel, if you purchase used, that you research the RV’s maintenance records as much as you can. Even when they’re well taken care of a lot is asked of these machines and they’ll go downhill quickly if not properly maintained.
Steve