Just got back from round trip Niagara Falls to Big Apple and back.

Decided to have some fun with mileage tests.

From Buffalo to Syracuse, set cruise control to 70MPH. got about 52.5 mpg. about normal for me.

then from Syracuse to Albany, dropped cruise control down to 60MPH. Mileage went up to 59MPG.

OK, now I get off the interstate at Hudson, NY. Cross over the river and get on the Taconic Parkway. Still limited access highway, but slower speedlimit. So now I set cruise control to 50MPH. Mileage goes up to 63MPG!!!

All above driving done under identical as possible circumstances, road conditions, terrain, weather, car cargo load. so only variable should the the speed.

Including some driving in NYC, then back across PA hills, total trip mileage 53.4mpg.