Poor MPG when hubs locked

[MythX]

Here in Colorado, we had some cold/icy weather the last couple weeks. With some roads fine, and others icy, I decided to run around with my hubs locked so I could have push button 4wd capability. Everything seemed to work just fine, when others were stuck going up hills, I had no problems getting by. However, I filled the tank the other day, did the calculation and only got 12.3 MPG on that tank. I suspected it wouldn't be as good as normal, but normal is 17.8MPG. Is this expected? Or is this indicative of a problem? Where would I begin looking? Differential? T-Case?

Truck is a '94 sport 5-spd. Stock except for the manual hub locks.

Thanks

 

[Karpov]

My winter average mpg is 17,5, 14,5mpg was highest when i drifted etc.

4wd on, with automatic (should consumpt more than manual).


Temperatures outside about -5 to -30 celsius and allways cold starting without blockheaters etc.



So i dont know about low range but its not impossible.

 

[RangerX]

Driving with hubs locked and in 2wd does cause extra drag on the driveline. I would not have guessed it affected mileage that much, though, but I don't think there's anything wrong.

 

[jd4242]

Its expected you would get worse gas mileage. you are now spinning the front axles and gears.lot more resistance, plus factor in that you used 4x4 some..17 is REALLY good if that's what you were getting around town...

 

[malohnes]

Temperatures also affect winter performance and mileage, not just locking the hubs. I get anywhere between 10 and 15 depending on snow conditions and how much cold engine driving I do, as that greatly affects mileage. I too have been surprised at the mileage drop for just engaging the hubs, but that is how it is. I try to never drive the truck until a couple minutes of warm up happen.

Maybe it is time to give the ole drivetrain a look see in the springtime and replace old gunned out and dry u-joints and repack bearings!

 

[MythX]

Thanks, glad it doesn't seem to be a problem. Thanks for the input. We have another system coming through soon, I'll try and pay closer attention to the MPG, get some real metrics.

Thanks

 

[4x4junkie]

Yea colder air is denser too, so your engine pushing your truck through it uses a little more gas.
Combine that with your gear & engine oils all being thicker, the longer time before the engine hits operating temp... It all adds up.

(the colder air alone is good for a 2 MPG drop vs during summer temps).