If you had a do-over, which would you get?

Just sold my Ford v10 based rv last year and bought a Mercedes based class c. Never in 89,000 miles did I ever do a thing to the engine other than oil and filter changes. Mostly I could do about any mechanical repair to this thing short of a transmission rebuild. I'm shocked that people call this engine a gas guzzler. I was getting anywhere from 12-14 mpg. My Mercedes 3500 class c averages about 14-15mpg. To be fair, the mercedes rv is about 3feet longer but still! Hands down, the Ford v10 is the best and this is the first and last Sprinter.