There is a major problem with a bed cover though. You walk up to your truck toss something heavy over the side and into the bed of your truck and you now have a big hole in that expensive fiberglass bed cover. Or at least a really bad scratch.

A bed cover kind of defeats the purpose of a truck, I never really understood them. If you need to cover stuff a van would be a better choice.

 

and you can't chuck empty beer bottles out of the cab into the bed at stoplights...I've got the process down to an art and it messes with me when my tonneau is on

 

They shouldve done a test where they took the tail gate off completely, that wouldve changed the drag significantly.

 

Actually when I had my '96 RAM that had a nice, one-piece bedliner in it, having the tailgate down was a must at highway speeds. It wasn't because of mileage, since I already knew having it up didn't reduce MPG, but it was because when up, travelling at about 55MPH or more, the rear lip of the bedliner would start catching the buffeting air underneath it, causing it to actually lift up from the bed of the truck and pull the sides inward, creating this crazy, bowing, flapping monstrosity that you could even see from behind. It looked pretty funny and scared the crap out of me the first time it happened.

 

Also tested by the MIT 2.009ers except the used a wind tunnel with models. They found that bed cover with a small wing lip was most effective. Raised the bubble higher above the bed to creat a smaller coeffient of drag.

 

The empty beer can flip is a skill that I am still working on. It's not easy as it sounds, especially with a little cross wind. I usually sink it, but I still get covered in suds from the bottom of the can/bottle once in a while.

 

I run this tailgate so that I can see my boat when I back down a couple of boat ramps which are pretty steep. There was no gain or loss in MPG. I drive like an animal though so I'm not sure I am a good example.

[IMG]local://upfiles/18043/47653EFD70EB4ED9A98CB78130CF77C2.jpg[/IMG]

 

Now that's a fine piece of tail (gate)!!

 

If someone from MIT actually tested and found that result with pickup tailgates, please post the link.

Some engineering students from New England College won a ASME (American Society of Mechanical Engineering) prize for this study on a scale model of a 2nd Gen Ram in a water tunnel:

http://web.archive.org/web/200304141...affner/did.htm



Their results are very similar to the Mythbusters results, except that they found that removing the tailgate hurt drag, whereas lowering the tailgate slightly improved the Cd but to such a low extent that it would be hard to detect with anything but the most sensitive of tests.

I thought the Mythbusters episode was 'reasonable' as entertainment,
but running completely out of gas is a poor way to accurately test MPG - although it adds to the drama of a TV show.

When the fuel pump loses prime and starves the engine is pretty variable, and you could not count on one truck dying with exactly the same fuel left in the tank as the other truck. It could easily vary by 1-2 gallons.

Off camera the Mythbusters crew may have checked the two 'matched' Ford trucks over similar 300 mile test runs to see that they were indeed about the same MPG.

The 18 wheel truck industry has been tackling the problem of doing good MPG tests for several decades and in the Society of Automotive Engineers/Truck Maintenance Council Type IV test the standard proceedure is to take two nearly identical trucks and run them as a pair across the highway test run distance AT LEAST THREE TIMES before modifying one of the trucks and doing the real test to see if a mod improves or hurts MPG.

In the SAE/TMC Type IV test they also recommend doing another 'double check' test where you swap the mod onto the other truck that had been un-modified on the previous run.

In the case of the Mythbusters test of the Fords, to really nail down whether the tailgate down helps or hurts they should have done the test again, this time with the truck that had first trip had the tailgate down now traveling with the tailgate up, and the other truck previously with tailgate up now travelling with tailgate down.

But hey, its a TV show on a budget with time deadlines....you can't expect them to do it completely right.

 

Truck magazines have tested this and found no difference, as well. At Bonneville, Salt Flats racers always use a tonneau if the rules allow or get creative with the rules and fill the rear two-thirds of the bed with an "intercooler tank," as GM did with its record-setting S-10 some years ago.

The moral, cover the bed, leave the gate, and do less damage to your bed.

All the best.