Bob I believe it is a 2.47 or something like that. Remember, these cars have a 4 speed trans but is not overdrive. cjlipps mentioned Buick 3800 running 2000 at 70, but that is an overdrive trans. We had several customers that had 3800 Olds and Buicks that would get over 30 mpg.
Other cars I have had also got lower mpg at high speeds. This car is different, and the only one I have ever had like it. I can fell that the torque comes on at around 2500 and pulls hard to about 4000, so It must be at the bottom of the torque peak at 75 mph (2500 rpm). Which is good and bad. Good if on the interstate, bad if on state roads at 55 mph. Maybe 3rd gear if lower than 60. I have tried to explain "the sweet spot" of an engine. Every engine has one and it may be different on the exact same engines. I understand frontal area and CD but it comes down to how the air goes around, under, over the body. If this car was designed to have a max sustained speed of 145 mph then the engineers took that into account when they built the car. I think they did a good job. I shouldn't mention this but this car really smooths out at around 120. It is still responsive at that speed but I am sure the mpg is down a tiny bit. Like I said before, when they finish the bridge over the big pond I am going to Germany and check the mileage at 140mph. Ha HA.

Paul

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84 500 SEL (307,xxx miles)