Drag

kksiu2002 · Mar 14th, 2004, 01:50 AM

Is it true that the bed of a pickup truck creates a lot of drag? I mean, will I see improvement in fuel efficiency if I drive on the freeway with the tail-gate in the down position? Also, is it legal to drive with the tail-gate in the down position in Texas? Moreover, what is the optimant speed to drive on the freeway if I want to get the best MPG on a 4 banger Frontier with 5 speed? Thanks!

Phyroinstinct · Mar 14th, 2004, 08:24 AM

If you read this forums all the way through, it is discused in it.

http://www.nissanforums.com/showthread.php?t=47295

jadcock · Mar 14th, 2004, 08:59 AM

In general, the slower you drive in top gear, the better your mileage will be. I use 5th gear as often as I can. Many of the roads around here have a speed limit of 45 mph, and at that speed in 5th, my engine speed is around 2000-2200 rpm...pretty good for gas mileage. If I get out on the Interstate, and drive 70 mph, the engine speed is up around 3000 rpm...not as good for gas mileage, but I have no choice, as there's no 6th gear.

To get the best mileage, drive in the highest gear you can reasonably drive in. Nissan actually recommends (this is for '95 models) the following speeds as shift points:

1-2: 15 mph
2-3: 25 mph
3-4: 40 mph
4-5: 45 mph

That shift schedule produces an upshift when the engine is in the 3000-3500 rpm range. I usually shift a little sooner, when I can. I'm usually in the next higher gear somewhere between 2500 and 3000 rpm on the tach. This is all everyday driving, mind you. Out on the Interstate, I'll be in 4th gear sometimes to pull some of the hills, and that's a sustained engine speed of 3500-4000 rpm sometimes -- pretty poor for mileage. But sometimes you gotta do what you gotta do.

2fastdre · Mar 15th, 2004, 12:17 PM

You can notice slight changes in gas mileage from such things as the tail gate or some kind of load tied to the roof of your car at highway speeds. Drag has more affect at higher speeds. I don't know about Texas laws about driving with your tail gate down, but if you try it - then make sure nothing loose flies out of your bed. And you can always replace your stock tail gate with one of those light weight slotted or net tailgates so the wind can go through it. Or you can get a bed cover or a topper.

And yes - the slower you go in top gear, the better the mileage. But if you are on a cross country trip, then it's hard to keep yourself going slower. Of course, there are people who take efficiency really seriously. I am a member of the TDICLUB.com and there is a guy who was able to drive 1400 miles on a single tank of diesel. It was an older Passat TDI and he averaged 58.2 MPG. You can find his thread from the main tdiclub page, but what he doesn't immediately state is that he also averaged about 55-60 MPH. Now - imagine driving 57 mph for 1400 miles.

2FastDre.

jadcock · Mar 15th, 2004, 12:52 PM

Here's a link to a discussion we had a while ago about tailgates and drag:

http://www.nissanforums.com/showthre...light=tailgate

Those air gates actually increase drag quite a bit. The best thing you could do would be to install a box above the bed that "swoops" down to the tailgate. A tonneu cover also worked well in that test.