When they rate fuel economy on a 4x4 vehicle, is that being tested in 4x4 mode? Does driving a 4x4 in 4x2 mode actually save any gas? Ive read both ways in that the diff and axles are still engaged, and therefore no fuel savings to be noticed in 4x2 mode.

 

In 4x2 mode, the front diff and front axle may still be engaged, but there is no load on them, so they should free wheel, so it should consume (just) a little less fuel to move. It would be better if you can unlock the front hubs as well, then the front drivetrain would be just disengaged dead weight.

 

got it. Thanks