Since I locked my hubs I have been getting on average 110 km's less per tank. I usually get around 390, but I dont even make it to 300 now. Is this normal?

Cory

Why not unlock them?

because the parking lot at the university is pure ice, as is the hill outside my house so I have to drop it in 4x4 if I want to get anywhere.

That is the ONLY reason I like the auto hubs! ;)

A 25% decrease in gas mileage? That seems excessive to me. I have seen maybe as much as a 10% decrease. What do others think?

I have had my manual hubs locked for extended periods of time and did not notice a change in millage...

Well if you've been having a decrease in gas mileage its not just the hubs being locked all the time you have been putting the vehical in 4x4 and going up hills I'm thinking thats alot of your decrease in gas mileage.

I usually see a slight drop in mpg, but nothing excessive. When where your U-joints last changed? If they are old and rusted then it will take more force to transmit power through them. How about the front diff fluid, when did you change it last?

Ive only owned the x for 6 months so I'm sure the U-joints have never been changed. The diff fluid was changed not too long ago. And I dont think that I drive it in 4x4 for long enough for it to make a diff, its only to get goin, then I drop it out. Ill do the U-joints on x-mas break and see if that helps.

Check out the link in my sig line on U-joints (it has lots of info and pics on how to press them out with a "C" clamp tool). I would also change the spindle bearing and and seals. The spindle seal (pressed into the spindle) is MotorCraft BRS-88 F3TZ-1S175-AA the bearing is $6 and very common as is the stub axle seal. The Haynes manual states not to remove it from the axle because a new one will need to be pressed on (its rubber with an embedded steel ring). This is no longer true as the new seals from timken are 100% rubber and fit on easily with no tools.

did you factor in the winter blend gasoline? i think this time of year is bad for all of us in the Northern states/canada

did you factor in the winter blend gasoline? i think this time of year is bad for all of us in the Northern states/canada
How much does it effect milage?

I've personally experienced a 1-2 mpg drop since the beginning of November...now that is HORRIBLE to me considering i only get 11 to begin with...

Others on the board have had similar drops in the previous winters...

How much does it effect milage?

It does affect it. 1-2 mpg happens to my 1st gen sometimes. Cold weather (meaning longer open loop (rich) operation) and winter gas do it. Your mileage drop is probably a combination of cold weather, winter gas, locked hubs, ice and hills.