I just completed a cross-country jaunt in my '48 pickup with the flathead V8. Trip went from nw Montana to eastern Ohio by way of Denver, Wichita and Kalamazoo, MI. The return trip was a little more direct. Total miles logged was 5,391 and averaged 15.7 mpg eastbound and 13.5 westbound (headwind). Used a quart of oil every 350 miles or so, and I dumped in a can of lead substitute every other tank.
Only significant problem was loss of one waterpump in central IL requiring overnight air shipment of a new one from Sacramento Vintage Ford.
Smoothest running engine I've ever driven across this great country.
Get those flatheads out and drive them!!
Rear gears are 3.50. I swapped in a 9" rear before the trip - lets me run about 62 mph @ 2400. Just have to accept the fact that everybody will pass you......on the oil, I can only say that it doesn't burn blue smoke and it leaks a bit from the underside.
I am running the original 3.73s in my truck... I'm glad to hear the MPG was as high as it was. The old train of thought when the flatheads were still new was "If it ain't burning oil, it ain't lubricating the engine like it should".