Anyone else getting BAD milage w/ the 4.0?


TexCaliBII

TexCaliBII

10+ Year Member

U.S. Military - Veteran
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Oct 6, 2010
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Palmdale, California
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88
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Guys,
Not sure what the cause is and looking for help. My 4.0/5 speed runs like a spotted ape, whatever that really means..., but since the cold (-30 to -50F) really hit up here the gas milage has plumetted. I know driving in extended cold will decrease milage but yikes mine is truly terrible, like 10-12MPH. I have double checked for vacume leaks, none; fuel pressure right on the mark; no codes; no CEL and no gas leaks. Anyone else on COLD climates suffering this too?
 
Stupid question is it running anywhere near a warm temp. My ranger is notorious for bad gas mileage in the winter because it doesn't like to warm up. LOL
 
Extended warm ups?
Overcoming extra friction re oil viscosity?
Extra fuel needed for start up in extreme cold?
 
Check tire pressure. The colder it is outside, the more the tire pressure will drop. My truck's tires dropped by 10 psi when the temps reached 15*. And don't forget to let that extra air out when it gets warmer again.

What kind of driving are you doing? If it's all short trips (10 miles or less) then I'd say your mileage is perfectly normal. My Explorer would always get about 12 mpg in the winter when I was commuting about 2 miles each way to school. Normal mpg for it is about 17-18 mpg.
 
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Dude, being in Alaska, isn't it ALWAYS cold there?

But I would agree with the above comments. If your tire pressure is still good, it could be a problem somewhere else on your vehicle. It's a Gen I (or Gen II), so its possible that something ELSE may be coming apart aside form your previously checked places. Then again, if there are no codes....*shrugs*

I usually like the Seafoam treatment from my brakebooster for my vacuum lines, the gas tank for a fuel line/injectors cleaner, and occasionally in my oil to remove some of the sludge before my oil change. Perhaps you could have built up sludge over the years in your crankcase, and it makes matters worse when its cold and the engine is barely up to temperature. You could try this, and change your oil. Mystery Oil also works really well. Let your truck warm up, idle, pour in the treatment, idle for 10-15 minutes, and change oil. I noticed a difference in my truck the first time I did it. Perhaps it could do the same for you with your colder conditions.

Mechanically, I dunno. You could check your wheel bearings for play since this causes a couple MPG. Really, it could be anything. It's hard to diagnose over hte Internet without being there and with minimal information, save for being "cold."
 
Everything I've ever owned always gets worse in the cold. I've always attributed it to the different fuel mixture. Now they've added ethanol in there, and it makes it even worse. In my F150, I've gone from 15-16 mpg's to 12.5-13 mpg's.
 
I miss my Nissan VQ35. I got at worst 20 mpg, 32 at best taking it on highway. For 250 ho v6 it was great. Also it only had 32k miles. At 122k with my explorer I'm getting an average of 15.9mpg in the summer. Bout 310 miles to a tank with stock tire size and 250-260 with my 265/75/16 BF Goodrich AT's.
 
All,
Thanks for the replys. No it is not ALWAYS cold up here, just every month that isn't Jun, Jul or Aug. Not worried about sludge as I took a good look at the motor before I put it in, valve cover gaskets, etc. And I run synthitic oils all around. Some might recall I was posting a year or so ago about my 4.0 install that would not start after sitting out in the cold so this truck got, and gets, seafoamed etc. I was defintiely thinking the extra run time for warm up, cold oil, square tires for a while till they turn round again but it really seems the milage is truly terrible. Mainly it goes to/from work here on base so less than 10 miles a day in slow driving. My 87/2.9 doesn't do this bad in the winer, though not a whole lot better. Even my Chevy does worse in the winter, even the thrid door latch doesn't function perfectly from the metal shrinking. I'll recheck the air pressure when I get back to driving. I took off the big mudders and am running 31" Revos now and they seem to stay up even when driving when it's really cold out. Forgot to mention that it also has a locker in the front axle and I keep the hubs locked. I did run it for a couple days without the hubs locked but it almost seems I can watch the gauge go down. :dntknw: Hopefully it all gets better as the weather warms up. And Texas winters will be WAY better on my trucks come next winter..:icon_bounceblue:
 
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Wait? You took your big tires off and put the 31's back on it?

Did you change out your speedometer drive gear too? That may be messing with your calculations.

But traveling less than 10 miles in slow traffic, in temps that low. Yeah, you aren't doing too bad on fuel for all that.
 
I get that kind of mileage when I city drive. Highways I still get 21 mpg.

I also drive the sh!t out of it cause its fun to drive.
 
Well I never "adjusted" it for the big tires. And yeah, the 4.0/5 speed combo is a blast to drive and I’ve been keeping my foot out of it as gas up here is nearly $4/gal. I've been careful of 1st gear too as I've done a couple 360 degree turns unintentionally even with the locker engaged and the LS rear diff. Thanks again for everyone’s inputs. As a side note it also seems the 88 w/ 4.0/5 speed is way lighter in feel then my 87 2.9/A4LD. Both have explorer axles and 4 wheel disk and 31” tires. Other than the drive train differences is the 87 has steel wheels and the 88 now has 98 Explorer rims. :icon_confused: :dntknw:
 
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Cold dense air combined with fuel injection equals more fuel to make a bigger boom in your combustion. This us why it runs so well but uses so much gas. Warmer less dense air requires less fuel to be at proper stoich this better mpg.
 
My BIIs (2.9 and 2.8) are winter drivers. I run them on 140 mile commutes each day. In the summer time I'll get 21mpg, in the winter, 14.5 - 15. That's on the highway combined in and out of 4x4 at anywhere from -25 to +20. Driving slower with shorter distances and locked in, I can see you getting that kind of mileage.
I can't accurately check the mileage on my '96 4.0/5sp because the odometer isn't functioning (speedo is), but because I run the same routes as I have been for 12 years, I'll say the mileage is going to average out similarly. This has been an unusually warm winter with very little snow here, so can't do apples to apples.

My son-in-law is an Alaskan native though. His family is now living in Anchorage not too far from you. I've been up there a time or two.
 
Has anyone taken into consideration that the A/C runs in the winter to dry the air in the cab, my Dodge was the same and it took me awhile to figure it out, so unless you disconnect it will continue to cycle with the defrost and possibly the heater. It is supposed to prevent fogging so it might be with just the defroster.
 
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