My mother in law has been driving her truck since she bought it used, with the lock outs in four wheel drive. Will that cause any damage? It was not engaged on the inside, but just curious. She bought it last summer I believe.

 

Nope, she just had crappy fuel economy... A few of the guys from the excursion forums leave them locked in all winter (regardless of snow or not). As long as the actual transfercase was not engaged that is.

 

I run mine (hubs) locked all the time
Only unlock them when I am going to be traveling on the freeway.

There is absolutely no measurable difference in fuel mileage .

 

Same here, never noticed a difference one way or the other.

 

I lost .5 mpg on a 1200 mile trip on my previous ex v10. Hand calculated.