OK, I've heard this one for years & years & years & years. Do you get better FE with the tailgate up or down? They just had it on Mythbusters and tested it.

What do you think?

'00 Insight "Wazabi" -75,000+ miles
'03 Toyota Matrix - 81,000+ miles
'03 HCH-CVT-OSBM-41,000+ miles (retired 04-10-06)
"I'm very secure with my little Insight, no Prius envy here."

You're going to get different results from different trucks, for one thing. All the major automakers want to be able to brag that not only does their truck tow more, have more power, and beat up all their competition's trucks, it gets better gas mileage too. As such, they put a lot of work into making sure the shape generally works well for fuel economy with the liftgate up. I've seen reports from engineers at two of the big 3 claiming their trucks get either the same or slightly better fuel economy with the lift gate up, and one independant test showing it was marginally better with the liftgate down. The one thing that's consistant is that a bed cover will significantly improve aero, and thus fuel economy.

Actually, I've seen a test without a tailgate too. Remember in the 80's when tailgate nets were huge. We sold a ton of them at my father's auto parts store, also sold lots of tonneau covers. Lots of aftermarket companies tried to have their claim to fame for truck FE improvement items.

'00 Insight "Wazabi" -75,000+ miles
'03 Toyota Matrix - 81,000+ miles
'03 HCH-CVT-OSBM-41,000+ miles (retired 04-10-06)
"I'm very secure with my little Insight, no Prius envy here."

Before my HCH, I drove a pickup truck. I got better FE (i.e. 16 as opposed to 14 or 15) with the tailgate up. There's a good reason for this that's grounded in physics:

You know that the area immediately behind the cab creates a nice low-pressure zone at speed. The rest of the truck bed is low pressure as well, and at highway speeds, the 'stagnant' air in the truck bed creates a sort of "bubble" of immobile air. The incoming air stream over and around the cab "sees" this still air as a barrier, and largely flows right over it as if it were solid - reaping some of the proven benefits that you get if you have a solid bed cover. If the tailgate is down or a net is in place, this bubble of relatively still air doesn't get a chance to form, and the result is a less aerodynamic rear half of the truck. I had a physics professor in college explain all this to me, and it sure makes sense. Anybody have a wind tunnel?

Before my HCH, I drove a 1993 Ford F150, and would get 14-15 tailgate up, 16.5-17 tailgate down, during the summer months. During the snow season, the tailgate was always UP so as to not let the snow blow out over other cars.

-Charlie...

I did not answer the poll because a couple of people have said sometimes having the tailgate reduces FE. I was lead believing a cover over the back was the best solution....

61.5mpg lifetime - 82mpg in recent months

Best Run >
www.cleanmpg.com

"fanatic" is what the lazy call the dedicated

i saw the show, so is it cheating if i answer the poll? it was somewhat painful to watch... 500 miles or so on 30 gallons of gas, i can go >600 on less than half that!

Yeah, no doubt. Even my 1997 non-hybrid Civic will do 400 miles on 10 gallons very easily. In fact that is slightly below my lifetime average for the year right now.

Hi All:

___Tailgate down here in the Ranger for the best FE. For anyone that owns a P/U, lay down in the bed while at steady cruise and you will find that there is no stationary bubble. You are in the worst buffet you could imagine and this includes below the side rails! If you don’t want to ride in the bed at speed (there are obvious reasons you wouldn’t want to), throw a layer of leaves in the bed. Maybe an inch deep should do it. Take off to steady cruise and only in the corners will the leaves just tumble over and over upon themselves. The rest of the beds leaves will appear to be in a margarita blender and will begin blowing out as if they were popcorn in a popcorn maker as time goes by!

___500 miles on 30 gallons of gas for 16.66 mpg? Ouch, that’s got to hurt

___Good Luck

___Wayne R. Gerdes

You forgot the poll option of, "don't know!"

I have no clue, since I've never done any personal testing. But, for 10 of the 12 years I've owned my truck, I've had a tonneau cover on it. So, the tailgate being up or down probably would not have made any difference at all!

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