I got 51.5 mpg from Escalon, Calif. to Los Angeles, Calif., going 55 mph in a 1999 Nissan Sentra 1.6L manual shift, with Tufoil in the engine. Air conditioner was on much of the time.
That's all freeway. In varied winding territory I get 45, such as Eureka, Calif. to Sacramento, Calif. Highways 101/20/16/5.