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Old 10-12-2020, 03:27 PM   #1
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Terrible Gas Mileage - Any mods that will help?

I've got a 2009 E350 with a UJOR 4x4 conversion and 6" lift. Running 285/170/R17 BFG KO2's. No engine mods that I'm aware of. I can't average above 10mpg to save my life, driving with no a/c on flat highways.


I've read many reports from others with similar builds who are getting better mpgs. I had the shop I use in Austin take a look at it and they basically said "It's because of the 4x4 conversion, just learn to live with it".



Hoping there are other options.
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Old 10-12-2020, 03:58 PM   #2
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What engine? What gear ratio? Have you had your van weighed?
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Old 10-12-2020, 04:08 PM   #3
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What engine? What gear ratio? Have you had you van weighed?
5.4L V8, 3.73 gears.


I have not had it weighed, but it can't be that much heavier than stock. All the rear seats were pulled out and replaced with less than 400lbs of flooring and build material. Those seats were probably 250lbs.


The roof rack, 2 100ah batteries and the ARB awning are around 100lbs. That's about it.
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Old 10-12-2020, 05:48 PM   #4
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Your problem is the 6" lift and 285 tires.

Distance between the ground and front bumper has one of the largest affects on fuel economy.

The 3.73 gears won't help either. That's way too tall for your tires, and it means you're not really taking advantage of overdrive.

Lastly, how fast are you driving? This is the easiest fuel savings.
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Old 10-12-2020, 05:57 PM   #5
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Your problem is the 6" lift and 285 tires.

Distance between the ground and front bumper has one of the largest affects on fuel economy.

The 3.73 gears won't help either. That's way too tall for your tires, and it means you're not really taking advantage of overdrive.

Lastly, how fast are you driving? This is the easiest fuel savings.
The gears are way to tall for my tires? Not sure what that means.


Plus, the tires that came on this thing when I bought it were 245/75/R17s and I was getting virtually the same mileage.


I try to keep the RPMs around 2000 or less, which is about 70mph, depending on the road and elevation. I'm not driving 85mph.


If changing the gears is a fix, I'll do that, but I started a thread about it last month and I wasn't hearing that I'd be increasing my mpg.
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Old 10-12-2020, 06:06 PM   #6
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Ditch the roof rack (if you don't really need it) and regear your axles to 4.56 and I bet you'll pick up 2-3mpg. Of course, the thousands of dollars that it will cost to do that may take a decade to recoup at the pump. Unless extending your total fuel range is the goal, it may not be worth the cost/trouble for you. The other upsides to the lower gears would be reduced stress on the transmission, less gear hunting, and better acceleration. If you tow at all, I'd say it's worth it.
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Old 10-12-2020, 06:10 PM   #7
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Ditch the roof rack (if you don't really need it) and regear your axles to 4.56 and I bet you'll pick up 2-3mpg. Of course, the thousands of dollars that it will cost to do that may take a decade to recoup at the pump. Unless extending your total fuel range is the goal, it may not be worth the cost/trouble for you. The other upsides to the lower gears would be reduced stress on the transmission, less gear hunting, and better acceleration. If you tow at all, I'd say it's worth it.
Most of the re-gearing cost seems to be labor. I spend a lot of time in Mexico, so maybe I'll look into finding a reliable Ford mechanic. I've got a guy that works on my Wrangler, but I don't think I'd trust him on an E350 re-gear.
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Old 10-12-2020, 07:11 PM   #8
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I dont disagree with re-gearing (certainly an investment)...it will lessen the stress on the drivetrain, allows an advantage when starting off the line, passing, and on grades. But, I dont believe you'll gain much in mileage since you'll be turning higher rpm's to go the same speed - Unless, as suggested, you slow down.
Admittedly I'm not one that puts much thought into mpg, and never approached my purchase with that as necessary criteria. So, IMO you're better off accepting what you have... a freedom you didn't before, and just get out in your rig every chance you get.
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Old 10-12-2020, 07:15 PM   #9
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I dont disagree with re-gearing (certainly an investment)...it will lessen the stress on the drivetrain, allows an advantage when starting off the line, passing, and on grades. But, I dont believe you'll gain much in mileage since you'll be turning higher rpm's to go the same speed - Unless, as suggested, you slow down.
Admittedly I'm not one that puts much thought into mpg, and never approached my purchase with that as necessary criteria. So, IMO you're better off accepting what you have... a freedom you didn't before, and just get out in your rig every chance you get.
Don't get me wrong, I love my rig, I just never imagined I'd be getting 9.8MPG. And that's before the CCV top goes on next week.


It just really blows to have a lower cruising range than a Tesla X.
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Old 10-12-2020, 07:51 PM   #10
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If it makes you feel any better, that same Tesla's cruising range becomes zero the moment the terrain has you locking your van's hubs. Probably sucks to sleep in too. Horses for courses.
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