Well, not all the time. If I drive at around 80mph, I get great mileage (about 30mpg). Yesterday on my way back to town on the freeway I had cruise set at about 83mph, and my mileage dropped to the low 20s. Its no big deal, I can just drive 3mph slower, but what would cause such a difference? It was the same road, 30mpg one way, 20mpg the other way. Would the secondaries being open at that rpm, ~3500, drop mileage that much? Something else I'm not thinking of?
