I have a 2000 tradewinds with a cat 3126 diesel. I tow a Mini Cooper and a scooter on the back and get 10+ mpg from it. The mileage is only 80k and it runs sweet. However, ALL engines have seals, rubber components and after 21 years they get hard, brittle and fail. I have just had the rear main oil seal replaced …… wait for it…….. $7500!!! This is not a DIY job so bear in mind the age, NOT the mileage is more than likely to govern what needs to be done.
However, the floor plan and quality of the motor home is unbeatable (in our opinion) and we expect age-related expenses to occur