it's not the rear end that is geared lower, but the tranny. the auto has higher gear ratios because the torque converter can unlock and slip allowing an effectively lower gear ratio. hence, part of the reason your buddy gets more mpg is that top gear in the auto is higher than top gear in the 6sp. the other reason is that the auto (or rather the computer) is programmed to maximize fuel mileage and most people that buy a manual do so because they like the control. in the manual if you start from a stoplight only to see the light up one block turn red, you will probably only make it into 2nd or 3rd and just push the gas a little until you get there to avoid shifting so much. the auto will most likely hit top gear by that time. this puts the rpm's very low, saving fuel but costing power. if the light suddenly turns green and you hit it, there will be some lag time while the auto downshifts and then revs up where the manual, already in the lower gear, will take off quicker. a bit long winded but mainly, the lower fuel mileage is because of the lower top gear and the fuel-efficiency minded transmission programming. i for one love my 6sp but then again, all of my 6 vehicles (8 if you count the mtn bikes) require me to shift. just never been a fan of the computer deciding which gear i need to be in (and they never seem to last as long as a manual).
