Heres the deal. My sister and I have the same truck. 2004 Eddie Bauer Expeditions. Both are 4x4 and both 5.4l. She followed us up north one weekend. We both used cruise control so we had identical driving situation. She only got 14.2mpg and I got 16.6mpg (actually calculating out the mileage) The only differance between the trucks is that I have 3.73 gears and she has had 3.31 installed several years ago. Do you think mileage will go up more on these with 4.10 gears?