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I have a 97 F350 4x4 crew cab; stock except for 3 inch down pipe. It has 3:55 gears, just changed from 4:10, 5 speed stick, K&N air filter. Tires are 285/75/16, it gets about 14 mpg at 70 mph - does this sound right? Seems low from what I have read on PSN. It does have some soot on fire wall so I think the up pipes are leaking. Could that be the cause of poor mpg? How hard is it to get these pipes out? Thanks for any advice you can give.

I also unplugged the waste-gate and it seems to run better.
 

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I have a 97 F350 4x4 crew cab; stock except for 3 inch down pipe. It has 3:55 gears, just changed from 4:10, 5 speed stick, K&N air filter. Tires are 285/75/16, it gets about 14 mpg at 70 mph - does this sound right? Seems low from what I have read on PSN. It does have some soot on fire wall so I think the up pipes are leaking. Could that be the cause of poor mpg? How hard is it to get these pipes out? Thanks for any advice you can give.

I also unplugged the waste-gate and it seems to run better.
There is no wastegate on these old trucks.


Sounds normal for the speed, soot on the firewall is leaking uppipes.
 

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Thats not too far off, Is your speedo calibrated for the tires? Take a GPS and see how fast you are really going if not, it could be a few mph off. But 14-16 would be close for a CC depending on how cold it is where you are.
 

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Beef
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Thats not too far off, Is your speedo calibrated for the tires? Take a GPS and see how fast you are really going if not, it could be a few mph off. But 14-16 would be close for a CC depending on how cold it is where you are.
good point.
the cold will kill your mileage.
leaking uppipes will mess w/ the turbo spool and that could be causing you to give more go-pedal in response to the lack of turbo spool.
 

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also winter fuel right? i have heard that it plays a 2-3 mpg diff.
 

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:whs:
winter fuel regularly drops my mileage by 2-2.5...
also, I know it sounds like an awfully small change to make a big difference, but slow down to 65 if you can bear it.
Do you have EGT gauges?
 

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Check your brakes. Fords are fanous for dragging brakes.

Check your EBPV. Those things stick shut. Just like an exhaust brake.

Carefully driven (depending on terrain) that truck should give 17 easy.
 
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