[E. Pluribus Unum]

I commute 75 miles round-trip to another rural town five days a week.

If I drive 80 on the highway like everybody else, my Toyota pickup gets 20 mpg.

If I drive 60 with the tailgate down, I get 30 mpg on the highway portion, and 25 mpg overall.

That's the difference between burning 4 gallons a day, or three gallons a day.

I hate it, but I'm driving 60 now.

Not that I want the speed limits changed. I can drive more slowly voluntarily without making everybody else do the same.

[mc6809e]

If I drive 60 with the tailgate down, I get 30 mpg on the highway portion, and 25 mpg overall.

Try it with the tailgate up.

With the tailgate up, a large horizontal vortex of air forms behind the cab and improves the aerodynamics of the truck.

[Red_Devil 232]

Tailgate down to increase gas mileage is a myth!

The National Research Council Canada, Ford Motor Company, and DaimlerChrysler test this, and they've all come to the same conclusion: Driving with the tailgate down decreases highway fuel economy, and removing the tailgate usually makes it worse. In many instances, it also increases rear lift at speeds, an undesirable condition in a vehicle with only a third of its weight back there to start with.

Putting a tonneau or hard bed cover over your truck is the best thing you can do for highway fuel economy.