…I’ve heard people claim around 24mpg hwy out of these things but I’m not buying it until I see it for myself.
How?
My previous truck got 10mpg down a hill.
((88 F250 7.3, sterling 10.25 rear end (3.55?), C6.))
I don't believe it either unless you live in an super flat state with no stops for miles. The winning combo would be factory E-rated tires maxed out, 6.9NA, ZF5, 2WD, 3.55 gears, single cab, unloaded, with a perfect fuel system, perfect timing, perfect alignment, new air filter, greased driveline, windows up no AC and you'd probably have to be cruising along at 50 with cruise on or a very steady foot. A guy in a Facebook IDI group was trying to say he got 26+ mpg with 31" tires and a T19. I call absolute BS. If you can show me an IDI that can get 26+ MPG with no overdrive and tiny tires, i'll show you the Land of make believe.
Also, i'm not surprised you old truck was getting 10mpg. Those C6 really eat up the fuel. If they would have had a lockup converter they wouldn't get such terrible fuel mileage. I've got a C6 behind a 460 gasser and let me tell you you're lucky to get 8MPG on the highway, unloaded at 55-60MPH. It's normally about 5 in town.