Increased mileage while driving in 4WD.
 

I'm driving a 04.5 2500 and was averaging 12-14 mpg. I put it in 4wd to keep everything lubed and ran a bunch of errands when the mileage spiked on the computer to 21mpg. Is this normal? Is it ok to drive in 4wd for extended periods of time without doing damage to the transfer case and front end?

You should "never" run your truck in 4 wheel drive on dry pavement. If you did, let's hope you havn't allready done some damage. As for the increase in mpg. I think it would be a minor miracle to see added mpg in 4 wheel drive.

You are not going to hurt it just running down the road in 4wd for a little ways you will notice it big time turning sharp.

Look at it this way, You are already turning the front axles, The only way I can see it saving fuel IMO is that when you accelerate the front is being driven and not pushed to speed?? I would not drive in 4wd all the time because the truck is equiped with " part time 4wd" so I cant imagine it being designed to work some of the time let alone all the time. I have also seen transfer cases that wear out and that is during off road wheeling and that couldnt be much milage. I have rebuilt transfer cases and I have yet to see whats under my truck. So even driving on a long drive wit hvery little in the way of turns I could imagine the wear and tear would be beyond the savings in the mpg.

Calculate them by hand...The comp may be thrown off by the 4x4....not sure why, but the overhead aint too accurate anyway...

You're not lubing anything on these trucks in 4wd that isn't already getting lubed in 2wd. Everything turns regardless.

I would imagin that if you drove far enough to get a true mpg. Then you drove far enough in 4 wheel drive (on dry pavement) to do some damage. If it isn't going to hurt anything to drive it in 4 wheel drive on pavement. Would you drive your truck that way for a tank full of fuel and report back to us the findings? There are alot of people waiting to here "your" results. [laugh]

If you noticed I said for a little ways.He was getting his mpg info from the overhead not hand calculated.

Running in 4WD on dry pavement puts a lot of strain on the drivetrain, but it is not going to break it. If it can't take that then it can't take any off road use and something is ready to break anyway. The problem is severe tire wear, a LOT of added drag, worse handling, and the added strain on the system for no reason. These things will cause more fuel useage, not less. Better fuel mileage comes from less friction or less wind resistance, not more.

There is no reason to scare someone by saying something like he may already have done damage. No he didn't. And his mileage won't go up either.

Wetspirit

I think there was a thread somewhere in the 3rd gen area a while back showing a busted transfer case. The reason wasnt jumping, scraping or anything like that. The driver left it in 4WD all the time.

You will, w/out a doubt in my mind, get worse mileage in 4WD.

And could cause some damage to the drive train.

plus, never trust the lie - o - meter computer for mileage. Hand-calc it for accuracy.