[JL8Jeff]

You can never go off the location of the gauge, you need to fill it up and use the actual gallons at that point. Even then you should really have them stuff the tank since the first little splash will kick off the pump. Regardless, I would expect 30+ out of an M6 car. And 65 is too low with the 6 speed, you best mpg will be 70-75 mph if you can maintain that. My old 93 Indy Pace Car with the A4 and 3.23's got 28 mpg on the highway but that was with the LT1 and a supercharger so it's not a good comparison. A proper tune can make a big difference. My old 93 had an off the shelf SLP chip so I was happy with the overall driveability it had. That was running around 2200-2400 rmp's on highway trips so you can see where you're a little low from the optimum range which is around 2000-2200 rpm's on these engines.