70-75 MPH on flat ground with no wind translates into 45-40 MPG, which is why your MPG numbers don't change. At 55, you'll see 50+ MPG. At 65, you'll see 47-48 MPG. The motor trend article comparing 40 MPG cars had a graph showing "theoretical" mpg limits vs. speed. For the Cruze ECO MT, those limits aren't just theoretical - they're real. I compared what I see at various speeds and found they matched almost exactly with what MT showed.Same here. I can drive nicely enough in-town, with an average of speed typically 30-33 mph, to maintain a 40mpg+ calculated average at the pump. While highway driving should boost that significantly, I find that going 70-75mph to keep up with traffic actually skews my numbers a bit since my average speed goes up, but my fuel economy barely does.
I've also had to use A/C this entire last tank of gas, which I know will hurt my numbers quite a bit. I may have my first sub-40mpg tank in a long time when I fill up tonight.
40 MPG Comparison Constant Speed Chart Photo 13