I always saw a 1-2 MPG improvement when using my soft cover on my 97 2.3/5 speed.

 

Since the only thing the tonneau cover does is change the aerodynamic qualities of the truck, the best (and most expensive) way to check it is by putting the truck in a wind tunnel where a variety of tests at different wind speeds can take place under completely controlled conditions.

I have a soft cover and I notice a drop in mpg without it, but when I tried to compare that to having a tonneau cover, there was barely any difference (again, soft cover), but these conditions are barely controlled (same bit of highway, about the same load, about the same driving styles, but temperature, wind, etc are all different).

 

Yeah the fair goes both ways. We got the fuel efficient engine a duratec but it doesn't come with many options like 4 wheel drive or even the limited slip. And they haven't given the duratec v6as an option yet so people are wstuck with the tried and true but less efficient V6s.

Time was one could get a Ranger with the 4 banger and manual hubs and transfer--I regret ever selling mine. Would have got the same thing if it still existed especially with the more powerful duratec, but took the meager options available just to get the fuel efficient engine.

 

I have gotten over 30mpg highway. 2002 2.3 xlt 4x2 with k&n cold air intake, Flowmaster exhaust. sportmaster bed cover and 31 x10.5 tires. just kept tach under 2000 most of the time and kept around 60 mph. over 60 and mpg dropped.

 

I got about 1 - 1.5 mpg better with my soft cover. Once I got lifted and larger tires with steel wheels I threw mpg out the window tho.

 

on mythbusters they tested an f150 not a ranger, the cab and bed on an f150 is not the same as a cab or bed on a ranger the aerodynamics of these two trucks are different so forget the mythbusters stuff. on my ranger when it was stock would see almost 30 but i have the 2.5. now i have 31's and i'm lucky to see 22. depends on the truck and how you drive it, and i bet the cover helps cut down on wind resitance from the air coming into the bed.

 

I didn't notice any difference when I put mine on. I drove 1000 km last week and got 16 mpg overall. Which is exactly the same as before the tonneau.

It does feel like its got less drag though. Probably just in my head, but you never know.

 

I also noticed that when the cover has snow all over it, it still blows off from the back, towards the cab. So there is still a bunch of drag off the roof of the truck.

I don't think covering the bed makes the rangers aerodynamics any less brick like.

 

It might be (and probably is, based on what others have posted) different for 2wd and 4wd Rangers and probably different for the different motors too. I'm still getting better gas mileage with my tonneau on, but I have probably one of the most fuel efficient setups the ranger comes in(2005 2.3L, 5 speed, 2wd regular cab). A tonneau cover probably makes the most noticeable impact when the vehicle already gets very high mpg. It might not make any noticeable difference if the mpg already sucks.

 

I drive enough with and without my tonneau on to have never noticed a difference. The only thing I see a tonneau good for is keeping the bed covered from the elements.

This sounds like a myth for Mythbusters! Hey, they proved the theory of windows down vs AC on.

 

I also generally do 90% highway driving, so I'm at fairly constant speeds from 50-75mph and I never see a difference in my milage. I'm always at the same 100km at 3/4 of a tank, 250km at a half tank and 320km at 1/4 tank.

 

Can't say i ever really noticed a difference either.