MPG woes
I searched the class b forum for mpg related topics and found/read a bunch. First far trip on my class-B, 1990 Ford Econoline 250 Intervec Falcon with Ford's 5.8L windsor V8 No check engine li...
Forum Discussion
3 things affect mileage the most: aerodynamics, speed and gearing.
You can't do anything about the aerodynamics. Most trucks built back then were designed to run at the 55mph speed limit. However, engine speed will drastically affect fuel consumption.
Too slow causes lugging the motor, too fast puts the engine past peak power. Both conditions use fuel.
See if you can find out the rear gear ratio. It's possible the truck was built with a numerically low rear axle ratio, like 2:52 - 2:73. If so, the engine at 60 mph is running way too slow to use it's power and lugging the motor. That runs the throttle more open to keep speed up.
There are online calculators that will convert engine rpm, vehicle speed with tire size and give you the gear ratio.
For a heavy vehicle will poor aerodynamics a better ratio would be in the 3:30-3:50 range.
You can't do anything about the aerodynamics. Most trucks built back then were designed to run at the 55mph speed limit. However, engine speed will drastically affect fuel consumption.
Too slow causes lugging the motor, too fast puts the engine past peak power. Both conditions use fuel.
See if you can find out the rear gear ratio. It's possible the truck was built with a numerically low rear axle ratio, like 2:52 - 2:73. If so, the engine at 60 mph is running way too slow to use it's power and lugging the motor. That runs the throttle more open to keep speed up.
There are online calculators that will convert engine rpm, vehicle speed with tire size and give you the gear ratio.
For a heavy vehicle will poor aerodynamics a better ratio would be in the 3:30-3:50 range.
