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Discussion Starter · #1 ·
there is something seriously wrong with my dads '99 ram. the truck has less than 100k miles, completely stock, and the best he can get is 15mpg average. there has got to be something seriously wrong for a 5.9 CTD to be getting worse mileage than my 6.7 CTD

if you guys could give me your .02 on where to start, i would greatly appreciate it.

thanks!
 

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I had a '99, 5 speed, and got 18-20, at w/e time, towing or not. Check tire pressure, and air cleaner. Really look into a cold air Intake. There are plenty of threads about them. I have an AFE Stage II cold air, jumped my mpgs by 2 mpg.
 

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Discussion Starter · #5 ·
its auto. lets just say i don't think my dad has ever put the pedal all the way to the floor. he's not exactly an agressive driver.

i on the other hand is a different story.
 

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When my 5.9 was bone stock (except for a lift and beefy BFG m/t's), I averaged about 15.6 mpg on each tank... With not much highway use. Gearing will effect your mileage as well.
 

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a free flowing exhaust helps as well. just installed a 4" diamond eye ss turbo back on my 01 and gained 3mpg. hopefully get somemore out of it when i throw a muff delete on!! an afe intake gave you 2 more mpg? wow!!
 

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I was averaging a little over 14mpg before the exhaust
 

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yeah with an auto, and bone stock 15 mps is what i would expect if you have a 3.55 (what I had in my '99 5 speed) or 3.73 gear ratio. Tell him straight pipe, cold air intake, tire pressure check, total cost about $550 dollars and you should then get about 18+ mpg's. In my opinion.
 

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yeah i would say a BHAF, 4in exhaust, change fuel filter and some sort of small chip
 
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