So you bought a Raptor, (assuming) 6.2, (assuming) 4.10 gears, and you're trying to squeeze out gas mileage? Nice!

Now that I got that outta the way, LOL!

Odds are, higher gears are not going to net you any mpg increase at all. In fact, you may find the opposite. I went from 3.55's to 4.10's on my truck with the existing 33" tires and netted a solid and consistent 1-2 mpg INCREASE across the board in all driving conditions; point being you're probalby thinking higher gears will help your mileage, but that's not always the case. In fact, it's most of the time not the case, but there are variables.

That truck and motor combo is quite a monster and unique animal. Odds are, any higher gear change to attempt a mpg increase would have a negative effect on fun factor without achieving the original goal.

There is one fact...I will guarantee you if you made a gear change that did result in an increase in mpg, it would be so miniscule that it would never offset the cost of the gear change.

Mine doesn't matter because I didn't change my gears for the mpg; I did it for the fun factor and towing capability so cost is moot for my situation.

I may be wrong, and I may be out of line, and I sincerely apologize if I offend you, but on the surface it certainly seems like you bought the wrong truck for your needs. That thing's neither built for mpg or for low speed crawling it around a ranch.

 

I would keep that Raptor stock. There's nothing you can do that will improve the gas mileage noticeably.