ive had my 05 fx4 lifted 4.5 inches on 305/65/18s for a couple of months now and have noticed ive lost between 80 and 100 miles a tank. i knew i was gonna lose some mpgs but didnt expect that much difference. the salesman at 4wheelparts said to try the usual intake,exhaust, and programmer which i already had pryor to the lift except for the exhaust. would the next logical step be to regear? based on charts, it seems 3.90 gears would bring me back to stock performance(currently running stck 3.73). does anybody cut gears in this ratio for my rearend? how will it be performancewise? should i just go with 4.10s,and hows the performance with these gears? i would appreciate as much feedback as i can get

 

You did adjust the speedometer for the taller tires didnt you?

 

i did adjust the speeometer with my programmer.

 

Depending on the weight of the wheel and rim combo, I would consider going up to 4.56 gears. If you read through the gear write up at the top of this forum you will see tons of info to help you choose. On the second page is a lot of useful info on selecting the right gears. But to answer your question yes gears would help you pick up some more mpgs for your city driving, however on highway you might loose a little instead. Depends on how bad your gas mileage is. But from stock my highway went down about 1mpg, and my city went up about 2 or 3. I do mostly city driving so it was not a big deal to me.