C12 vs ved12
 

I currently own an international 9200i with a C12 cat, that has 1.1 million trouble free miles, and am debating on buying a volvo 670 with a ved12. The Cat is averaging 6.9 mpg. Should I jump to theVolvo, or overhaul my Cat?

Assuming your happy with the International, I would do an inframe on the Cat. Much cheaper than buying another truck that could have more problems than needing an overhaul,unless you are looking at a new one and that will be big bucks. MMM

To answer your question, a newer Volvo would definitely be a mileage improvement over an older cat. I don't have much experience with them as rvs, but with over 25 years trucking experience, the Volvo is much more economical on fuel. Other things to consider is that there are a lot of places that won't do engine work on a Volvo engine (we had a Volvo day cab with a ved12 with I-shift that got 11.8 bobtailing, 6.0 grossing 80,000lbs, and averaged 9.6 overall). With a Cat, you can get it done anywhere.