Gas mileage and shells

[lensman]

What happened to your MPG when you put a cap on your truck? I just put a Snugtop XV cap on mine. I only have 200 miles on it since and I just get the feeling that I've lost one or two MPG compared to no cap - and that's with the tail gate up. This cap is smooth, rounded and does not stick up above the cab.

[T'sTOY]

I have an above the cab A.R.E. MX shell, which is also fairly smooth and aerodynamic, but I noticed no real change in my average mpg.

[peid]

There are people who will argue this until they are blue in the face, but the fact is, no box cover will improve gas mileage!

That includes soft covers, hard lids, and full toppers. Years back GM & Ford both did wind tunnel testing to see how much of an improvement leaving the tailgate down or using one of those "air gates" actually had on the vehicle.

They both concluded that neither helped in gas mileage as the air actually passed over the top of the cab and over the tailgate, not actually get caught by the box.

I know, almost every manufacturer of these covers and shell CLAIM that they do, but how many of those have this very expensive wind tunnel testing equipment?

I have a soft cover myself but by all means did not buy it for improved gas mileage, but rather to protect things and conceal them from the prying eye.

If you wasted your money on a cover only to think that you will get it back by saving on MPG, you made a mistake.

[charlie]

I lost about 1mpg on the highway when I put a ARE wedge on.Not sure what I lost in city driving,about the same,I think.Charlie

[ChuckFundra]

My experience in 12k miles is about a wash.

I loose a little in the city because of the extra weight or the shell and carpet kit (about 300# total) and may have gained a smidgen on the hwy.

But like Pied said, I bought mine for secure storage, camping, looks, and my dogs love it.

Chuck

[SilverBeast]

I was always under the impression that driving around with the tail gate up, without any type of cover, will kill your gas milage

I bought a Tonno cover a few days after I purchased the truck, and had no chance to check MPG, before and after the cover was installed.

Gas is relatively cheap in NJ, averaging around $1.29 for regular 87 octane in the cheaper stations, to around $1.40 in places like Mobil/Exxon, Shell, Amaco etc., so, it does not hurt to lose out on MPG, but have the awesome power from the 245HP engine

Cheers

[Rlockyer]

Originally posted by SilverBeast
I was always under the impression that driving around with the tail gate up, without any type of cover, will kill your gas milage

Try it. Drive a regular course, out and back (to equalize hills and wind) at a constant 70mph.
Tailgate up, tailgate down.

I read a report that there was a SLIGHT improvement with the tailgate removed or down, but in some cases it was actually WORSE with one of the cargo net style tailgate replacements.
The explanation given (or conjecture) was that with the tailgate up, air pressure built up in the bed forming a boundary layer of stagnant air, allowing the air moving over the cab to "ride" over the bed.
With the tailgate down, everything obviously dumped.
With the net style tailgate installed, pressure was not able to build up in the bed, but a "sail" with an area nearly half that of the tailgate is now in the stream.

[lensman]

Well, I didn't expect higher gas mileage. I'm just hoping I don't take a hit. I had a Tacoma with the small 2.4L engine. I could FEEL the different a shell made on that car. It gobbled up some power - like I was going into a mild headwind all the time. Of course, it's hilly around here and maybe it was just the extra weight taxing that puny engine. So far with the Tundra (300 miles mixed) if there is a difference it isn't much.

[TundRoss]

I'm pretty sure that you'll find that the covers don't increase mileage to any noticable extent. they may on paper by.001%, but in the real world, you would be hard pressed to see it. as a matter of fact, since my current ARE cover weighs 150 lbs, I'm fairly sure that I'm knocking the mileage down even more. I bought my oroginal tonneau, and the hard cover mostly for looks, and to provide a larger "out of sight" storage area.

[molecule]

I gained about a mile per gallon with the installation of the Snug top on the road average about 18.4 .

Bill

[fastmhz]

Originally posted by molecule
I gained about a mile per gallon with the installation of the Snug top on the road average about 18.4 .

Bill

Hmm..could explain the reason why I see a lot of tundras with camper shells now...

[lensman]

Bill

I gained about a mile per gallon with the installation of the Snug top on the road average about 18.4 .

What model Snug Top is it?

[molecule]

The Snug top is the Expo model , The info was in my sig. but just noticed it's not there anymore , Will have to fix that .
Bill

[Thwarter]

I didn't notice much change after adding my SnugTop Hi-Liner. It's higher than the cab by about 4 inches.

I'm planning on getting a boot for the space between the cab and shell. So far, I like the one from Truck Tunnel. We'll see if that may save any MPG, I think I'm getting drag in that space.

[lensman]

I tend to agree with Peid that the effects of a top are minor. I really doubt a boot does anything. Well, it will wear a ring in the cab paint where it touches - you know that? I worried about the full top because it removes the two step approximation to fast-back (aerodynamic) that a truck has. Peid, do you have a reference for the research you mentioned? Still, the drag is probably dominated by the frontal area and shape which is constant.

About the crack. I think if there was significant drag here you would hear it. I mean a lot of air would have to be blasting through there. You would hear buffeting/sucking/wind noise back there. I'm going to experiment by sticking some pieces of foam in the crack. I can determine ahead of time what force is required to move them. After driving around for a while I will see if they have shifted or disappeared