I have a Roll & Lock tonneau cover and I keep very close eye on my mileage. Not only do I check mpg every time I fill up, but I also have a scangauge tool that I use to check trip mileage, short or long with too. I have ran with the cover pulled out and the gate up and with the cover rolled up and gate up, down and even with the gate off. And from my experience, the only thing that seem to make any difference in the mileage is driving habits and conditions. I live where it gets very windy a lot and that usually has the biggest affect on my mileage. If your looking to get a cover to help mileage, your probably not going to see much if any improvement. You can swing mileage 1-3 point either way with just drive habits and conditions.

 

I average 13 city/hwy. I have a soft tonneau cover.
Either we have super crappy gas, or my truck just sucks when it comes to mpg.
It's an 05 GMC Sierra Z71 extended cab w/ 3.42's even.

 

I may get about a mile better.

 

No difference here I have soft tonneau and allways check my mpg.

 

I drove from Ohio To D.C. 3 times in a month. Tried the tailgate up, and down,
No difference. seems like the tailgate down would help. But it didn't.

 

I get 16.5mpg...i have a front end replacement RH bumper, and stock 265's. But i also have fipk and jba catback and a somewhat light foot. This is on a 200 mile trip goin up n down I10 between Houston and San Antonio.

 

Well, I am going to the track this tonight to race so I decided to go ahead and take my tailgate off and leave it at home. I drove to work this morning And my drive to work is about 30 miles one way. Most of which is highway driving. watching my drivers info center, which, granted isn't the most accurate form of calculation, it actually seems like I was loosing gas mileage rather than gain or stay the same. Now in this I cannot account for wind direction and speed. But I watch this closely everyday and normally in the morning at 75 mph I get anywhere from 18-21 mpg on the DIC. Today is was ranging anywhere from 15-19 mpg. I will check on the drive home and see how it reacts, there is usually a strong headwind on the drive home, so that might be the true tale.

 

keep it under 2k you will see a big difference.........but i did see a slight difference in mpg with my cover but i run 80 mph everwere i go to...i heard a heavy cover can hurt mpg worse though...a stepside i dont think would help to much with it down since the tailgate isnt very big.....i know i could go a day longer before i filled up in the truck with the gate down than i could up before i filled so i guess it had to be better

 

I saw a difference of 1 mile more. If you are looking for a soft cover the access roll-up is the best cover I have ever owned. Especially if you live where the weather and temperature change drastic.