[Backtobasics]

I really think you need to explore the water and methanol side of things. Snow is a big name, and they are doing a lot of advertising touting MPG gains. They also see a moderate 50-60 HP gain, but the breadth of their benefits in diesels is MPG.

With the 4.10 gears, you are turning more RPM. Slow down will pay divedends. Diesels make best MPG at or near their peak torque RPM, so find out what that is and stick close to it.

How about air intake modications?

If memory serves there have been some Diesel magazines that have seen HP and TQ gains + MPG gains, going to one of the upgraded oil pumps, and a set of performanc injectors. Yes, generally these are performance modifications, but increase in injectors is usually increased pressure and spray pattern, which should have better atomization and can equate to better MPG, if driving correctly.