Does this really help your gas mileage go up by 20%. How much increase in MPGs have people increase

 

I've seen about a 2mpg gain... its not much but it does help

 

so little it doesn't really count, i got one to keep my bed dry. 20 % is crazy and more of an urban myth than reality.

 

It might go up a little bit, but not 20%. If you are getting 15 mpg a tonneau will not get you 18 mpg just like that (that would be 20%). Maybe an exhaust, cold air intake, tonneau, and a very conservative driving style will do it, but not a tonneau itself.

In case you didn't know, trucks create a spinning mass of air behind the cab in the bed, this way, the air flows over the cab and then across the spinning mass of air behind the cab and over the tailgate, hence why you get better mileage with the tailgate up rather than down. This is also why if you have leafs in the bed and you open your rear slider you get attacked by them (lol...happend to me today)

 

If you drive strictly on the interstate, I saw a little help, but for speeds under 60, virtually nothing...

 

I saw nothing when I got mine!

 

Same here, had no change in city or highway MPG.

 

I had to deliver an engine acouple months ago. it was a 2 hour drive on the interstate. I got 20mpg and on the way back with the tunno cover done up I got 17mpg. but it could have been that I was driving slower with the 700lb engine in the back.

I really dont notice a diference with everyday driving. my wing though. I notice a good 1mpg less...... but it looks too good to take it off lol

 

It's actually better to leave nothing over the bed of your truck MPG wise. It is actually better MPG with nothing over it because the wind circulates in a circle in the bed causing air to flow over the cab and on top of the air circulating in the bed, so there is no wind resistance against the tail gate, everybody just thinks there is.

 

Not true man... There have been lots of tests done for this senerio, I believe they did this test on mythbusters a while back (episode 64), same truck, same road conditions, same amount of gas, same driving style and what they found from doing that test is:

Tailgate up is better than tailgate down. - For the reasons stated above better aerodynamics
No tailgate i better than tailgate up - While it has worse aerodynamics, its alot less weight.
Bed Cover is Equal to if not better than No Tailgate - improved aerodynamics (less drag)
Mesh Tailgate up is better than Bed Cover - Same aerodynamics as tail gate up plus the bonus of the less weight because of the mesh tailgate.