Originally Posted by BetaDnB
The MTX75 gets it's best mileage at 40 mph (5th gear) at over 60mpg. Somebody had posted a scan gauge graph at one point and I have also tested it.
Yes but this is in a 5MT, not a 6DCT, the dct would be spinning at 1825 rpm in 5th at 40 mph and only 1476 rpm at 40 mph in 6th gear. That is a delta of 349 rpm between 5th and 6th gear in the DCT, that can make a fairly large difference with enough distance run at that particular speed.
The 5MT would be turning over at 1690 rpm or so, which means that at 40 mph the 5MT has an advantage over the DCT locked in 5th, but not over one thats utilizing the 6th gear ratio. The DCT would still be more efficient in 6th than the 5MT in 5th under ideal conditions. However in the real world it may not matter.
All gear ratio calculations were done using the 16" wheel's rolling radius (17" and 18" are almost the same, the 15" is a little bit different, but not enough to sway the results)