Re-gearing for better MPG?? - PowerStrokeNation : Ford Powerstroke Diesel Forum
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post #1 of 20 (permalink) Old 12-08-2014, 04:58 AM Thread Starter
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Re-gearing for better MPG??

I have a 2012 F-250 with mini max, s&B intake fully deleted with a 4" and just put 35's on 22" fuel lethals. I was running stock wheels with 35" Toyo mt's and getting a good bit better mpg. I know the wheels and tires are alot heavier but I was trying to think of options to help improve it again. So I was thinking about new gears. Mine has the higher gears from factory. Any advice or experiences in this area would be greatly appreciate or maybe some other options.
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post #2 of 20 (permalink) Old 12-08-2014, 05:17 AM
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Re: Re-gearing for better MPG??

its going to take a while to offset the cost of regearing for fuel mileage...

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post #3 of 20 (permalink) Old 12-08-2014, 05:23 PM
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Re: Re-gearing for better MPG??

It all depends on how much you drive your truck.

If your truck is a weekend toy, you'll never pay for re-gearing or an overdrive.

If it is a daily work truck that spends most of the day parked at a work site, you'll never pay for it.

If you drive it 25,000 miles a year like I do, you can pay for damn near anything.


Speaking to the original question...yes changing to numerically lower gears will improve your MPG, all else being equal. It works by reducing the "engine frictional HP" at a given road speed. EFHP is somewhat of a misnomer. it doesn't mean bearings and lubrication but rather the work needed to move air and exhaust gas in and out of the engine.

Re-gearing both at the drive axle and by adding an overdrive work very well for me.

2000 F-350 SC 4x2 6 speed
3.08 gears Gear Vendor Overdrive
Slammed 4"
Rugged Air Dam
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post #4 of 20 (permalink) Old 12-08-2014, 09:00 PM Thread Starter
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Re: Re-gearing for better MPG??

I got the truck first of February with 40k on it right now it's at 75. I do ALOT of driving. Are there any other options besides gears ? Or have I already done everything I can ?
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post #5 of 20 (permalink) Old 12-09-2014, 09:18 AM
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Re: Re-gearing for better MPG??

the bigger tires are not helping you. Bigger tires/wheels take more power to rotate. Wider tread contact patch also increases rolling friction.
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post #6 of 20 (permalink) Old 12-09-2014, 05:21 PM
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Re: Re-gearing for better MPG??

What can you do?

Replace the big meats with OEM-sized rubber. OEMs use the lowest rolling resistance tires they can find. Generally a quieter tire is a more fuel-efficient tire.
Clean up your aerodynamics. Hereís an example. What A Difference Aerodynamics Makes - Part 2 : EVWORLD.COM
Get a 203 degree thermostat. I gained 1.0 MPG with just that little change.
Disable your EBPV. The darned things stick shut and itís like driving around with an exhaust brake.
Check your brakes. For some reason, Super Duty brakes have a way of not releasing properly.


Change your driving habits. Read this closely. Beating the EPA - The Whys and How to Hypermile - CleanMPG Forums
I donít necessarily agree with this dudeís politics, but folks, heís got the goods when it comes to driving technique. Just staying heads-up and staying off the brakes will help a lot. I have been called Sir Coastalot. Coasting uses energy youíve already paid for. Timing lights is powerful in the right situation.

Obviously rolling coal and good MPG are mutually exclusive.

Donít let the truck idle to warm up more than fifteen seconds. If your engine is running, youíve got oil pressure. Warm up the engine with light load operation. That will warm it up quicker anyway.

Read the stickies. Thereís a lot of good information there.

2000 F-350 SC 4x2 6 speed
3.08 gears Gear Vendor Overdrive
Slammed 4"
Rugged Air Dam
315,000 miles
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post #7 of 20 (permalink) Old 01-30-2015, 11:57 PM
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Re: Re-gearing for better MPG??

another great post dave,

I did have a question about the t-stat.. i though i had read the IH engines used a 205į t-stat vs the 203į. But still good to hear of teh MPG increase going from 195į to 203į. (the degree thing is alt+0176)

I try to coast as well, but find with the TC locked up when you get off the pedal and the engine goes to idle it will slow you down like crazy. I tried just putting it into "N" and man that thing will coast then. When i am coming up to a stop light I jump off the "gas" and let it slow and push OD button to down shift to help slow to save the brakes.

I had a 2008 chev impala that was a good coasting car for sure.. not sure how the trans and TC lock-up works different than the truck. They use a 4e60 I believe trans FWD.
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post #8 of 20 (permalink) Old 02-01-2015, 02:42 PM
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Re: Re-gearing for better MPG??

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Originally Posted by carl2591 View Post
I try to coast as well, but find with the TC locked up when you get off the pedal and the engine goes to idle it will slow you down like crazy. I tried just putting it into "N" and man that thing will coast then. When i am coming up to a stop light I jump off the "gas" and let it slow and push OD button to down shift to help slow to save the brakes.
You can also tap the brake pedal to unlock the TC. Not hard or far enough to engage the brakes, just to move the pedal enough to actuate the brake light switch.

What I don't know is if the computer will try to lock it up again after coasting for awhile.

Also, I think it is illegal to coast a vehicle in neutral. This may just be a Texas thing though.

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post #9 of 20 (permalink) Old 02-01-2015, 04:24 PM
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Re: Re-gearing for better MPG??

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Originally Posted by leojr View Post
You can also tap the brake pedal to unlock the TC. Not hard or far enough to engage the brakes, just to move the pedal enough to actuate the brake light switch.

What I don't know is if the computer will try to lock it up again after coasting for awhile.

Also, I think it is illegal to coast a vehicle in neutral. This may just be a Texas thing though.
I tried the brake tap thing and did not see to help.. I guess the low rpm of the motor is one reason.. on my torque app it shows being in 4th gear as well.

good thing i don't live in TX as i have been known to kick my 1992 sentra into "N" shut off the engine and coast down the hill.. the steering gets non powered but not bad and the brakes will work if i don't push them and loose the vacuum.. till i need them. a lot of hypermilers do the same thing.

plus how the hell is a State trooper going to know you are in N and most of texas is FLAT.. :) so coasting is kinda hard to do.
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post #10 of 20 (permalink) Old 02-02-2015, 04:12 PM
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Re: Re-gearing for better MPG??

Re: Post #8

"...I think it is illegal to coast a vehicle in neutral."

Such laws are unenforceable as a practical matter. How could anybody tell? It may be an aggravating factor in a wreck litigation, but idea is to not have wrecks.

2000 F-350 SC 4x2 6 speed
3.08 gears Gear Vendor Overdrive
Slammed 4"
Rugged Air Dam
315,000 miles
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