I don't think so but it's hard to tell. I suppose it should actually increase MPG because the tcase swap will allow you to be in real 2wd instead of always in awd. I did a lot of the modifications in a relatively short time period. I may have only gone thru one tank of gas before I lifted it and put bigger tires on it. The MPG changes were mainly from going up to a larger tire, and then again when I changed axle ratios. I don't think the tcase had much to do with mpg as far as general commuting.