i have a 2001 dodge ram 2500 5.9L v8 magnummanual trans.

i drive about 400 miles a day at 65mph-80mph and only avg about 13MPG i have stock tire size on it and the axle ratio is 3.55:1 as far as i kno i bought the truck used, 1st gear redlines at about 9mph so i was wondering if anyone knew a good ratio to instal to get besster MPG if its only like 1 to 2 mpg then forget it im looking to get aprox 22-25MPG highway

 

You will never get near that MPG with one of these trucks.

13 acually sounds pretty good for your combination.

 

well lowering thee gear ratio should increase the highway performance and i kno nothing about the ratios i just want better then 13 whats the best ill prob get?

 

the bigest thing is i hit a cow with a kia rio and totaled it that car i filled up for less then 20$ a night and went on one tank this truck i fill up at 70$ and use a tank the rental car i used when i had the injectors replaced cost me 40$ i do this run 7days a week with max load on a sunday of maby 1500Lbs and during the week maby 300LBS

 

Welcome to DF.

Only way you're going to get in the 20s with MPGs in a 2500 is if you have the Cummins diesel under the hood.

Best you can hope for, even with the perfect ratio, highway tires, etc. is maybe 1 or 2 more than what you're getting now, tops. 13 isn't bad at all.

 

Best thing you can do is keep it SLOW!!
Try going no faster than 65 for a week and i'd bet you will see a gain. Even better if you can go 55-60.
Remember wind resistance increases exponentially after around 60 IIRC.

I know it can be hard to go so slow, but if you really want so save a few bucks, it can be worth it.
Also, drafting behind semi's will do a little.

I think cruise control can actually decrease your mileage depending on the amount of hills.
Since cruise will want to keep speed up hills.

Also, I'm pretty sure my mileage increased with my superchips programmer on the performance setting (the overhead mpg gauge showed an increase)
But you have to run 89 octane of better, so there is a trade off.