Jan 31, 2016
The Best economy" is at 80mph DECELERATING down a hill" was true with carbureted vehicles. The idle jet would still flow fuel even if you had your foot right off the pedal. That idle jet is going to flow a drop every 10 seconds or so regardless, so it stands to reason that you won't get any fuel mileage parked, you will get the best milage at 80 mph idling down a steep hill!
New fuel injected systems will shut the fuel off 100% so this would not hold true.