My coach is a 1999 holiday rambler endeavor on a freightliner chassis. I've owned multiple gas coaches in the past. This is a major improvement over any of the gas rigs i've owned.
The 275 HP cummins is plenty adequate for the task. On mountain grades in between phoenix and flagstaff, AZ(large, long grades), even pulling a honda CRV, I never drop below 45 MPH.
Mine does have the "53 block" which was manufactured in brazil for a short period and they are known for cracking. However, if they are warmed up and cooled down properly this probably won't happen. Drive it like you want it to run tomorrow and you're good to go.
I average 10.5 MPG with just the RV cruising about 65 MPH. I towed my large flatbed the other day to the dunes and back, mostly flat and about 60 MPH. I got about 9.5 while towing. The transmission will downshift to 5th even on small freeway overpass hills, and if it needs to, it will shift to 4th. No need to be alarmed, these engines can handle RPM's with ease.
The other major problem on these generation cummins is the VP44 injection pump. The stock lift pump(fuel pump) is mounted on the engine and gets a lot of vibration. When it starts to fail, the injection pump will start sucking fuel instead of being supplied fuel from the pump. The outcome is never good and ends up destroying the injection pump. There are two things you can do: If you do buy this coach or one like it, put in a fuel pressure gauge you can watch while you drive. If it drops below 5 PSI your pump is probably weak.
Also, you'll want to run a fuel additive like power service to replace the sulfer they started taking out of the diesel fuel. I have had my coach for a year and half and I absolutely am in love with it. Feel free to PM me if you have any more specific questions.
