On the 08 Expy does the system engage extra parts when the system is on the auto 4X4 mode even though your driving on dry paved roads? I'm just wondering if leaving in Auto everywhere would decrease fuel mileage?

 

Using the 4x4 auto will decrease the mileage because of increased resistance from the gears being aligned and turning and occasionally even on dry payment the system will turn all four wheels versus driving in two wheel drive mode.

 

You won't notice a significant difference.

 

no noticeable difference on 2500 suburban in 4 auto, silverado in 4 auto and expedition in 4 auto. I find it highly unlikely you'll see any difference. Now, if it's rainy/snowy your fuel economy will go now no matter what.

 

I can feel the drag difference in 4Auto vs 2High so I leave it in 2High 98% of the time. Rain and snow she goes to 4Auto just 'cuz. The drag has gotta use more fuel and cause more wear.

My Explorer runs in 4Auto all the time, no 2High choice.

-- Chuck