No need to do all that testing Ben! Someone else already did, well I'd still like to do it with a C6 because it has that ridiculous OD.
Here is the link, scroll to page 26, graph 4.22 (gov site)
Not so interesting, most of the cars did best at 55 mph. But one car, the 97 Corolla did best at 60 mph. And it did 6mpg worse at 55 mph. Funny, I would have thought a little 4 banger would have been in the 55 mph category. In fact, it still did better at 65 mph than it did at 55 mph. And another funny thing, the 95 Geo did best at 45 mph and lost 5 mpg at 55 mph.
Unfortunately all of these cars were from the 80s and 90s. And the ODs of the 00s are much steeper. As you can see, the older cars tend to do better at slower speeds. And none of the cars tested were necessarily V8s. So if your car is on this list you're in luck, no need to buy a vacuum guage.
Best MPG Gov Testing
