Fuel mileage on these cars is a little funny. I've had mine since September '11 and have nearly 19K miles on it now. It's a stick. Overall mileage (calculated, not indicated on the dash) is right at 36.9 MPG. The car has seen about a 80-20 mix of city and highway driving.
I have found that the car (weirdly) gets better MPG in around town driving than on the highway. Typical in-town MPGs are in the 38 to mid 39 range, vs. low to mid 30s on the highway. I've taken three long trips in it so far - once from NJ to Road Atlanta when it had less than 7K on it. Using the cruise control I saw not one, but several tanks in the high 20's. The next longish trip (NJ to WDC) saw me not using the cruise, rolling along at 72 MPH, and knocking back 38. Last weekend we took it to NC (1100 miles round trip), drove it between 70-72, didn't use the cruise, and saw mileage from 36 - 38.
I drive it like a little old man - rarely if ever rev it past 4000, typically shift at 3000, and skip gears like a mofo. There's no need to push it harder - it's just noise, not power, after 4000 or so.
Observations:
1. Higher highway speeds kill this car. While it will run to 100 plus, and will cruise all day at 80+, given the 10 to 20% drop in mileage I've observed, it is obviously working very hard to do so. I'm not sure that the addition of a more overdriven top gear will help, because I suspect that would drop the engine speed so far below the torque peak that efficiency will drop even further.
2. Cruise control kills this cars efficiency, which is a first for me. As far as I can tell, the thing is so marginally powered at highway speeds that any grade requires a lot of effort to climb. Since the cruise only wants to continue at the given speed, damn anything else, mileage suffers as it adds more power to compensate.
3. This thing is WAY sensitive to gas quality. We've got four street vehicles (the 2, a '90 Miata, '04 E350 with the V10, and a '00 Corolla) to compare from. All are driven by the same two people. Only one (the 2) seems to have gas vary from tank to tank dependent upon where it was filled. The others are not nearly so sensitive. (We won't talk about the other "primary" '90 Miata that gets 10 MPG at the track!) On the way home from NC last weekend we apparently got a load of questionable fuel on I95 in VA. Mileage for that tankful dropped to 34, and the car exhibited a weird, barely detectable surge at part-throttle. I filled at the known good gas station near home and went back out on the highway with no detectable driveability issues.
