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Car Forum / Nissan / Nissan Cars / April 2008MPG improves on PU with tonneau cover?
The beginning of this month I bought a soft tonneau cover for my 97 Nissan PU, 2.4 l, 4 cyl FI, 62,500 miles. He's a good old boy and looks almost as good as when he was new. I buy him a present every once in a while. Last time it was a cat-back dual exhaust, and the time before that, a keyless entry system. When I installed the cover, I had about 3/4ths of a tank of gas left. Since driving it with the cover on, it seemed that my trip odometer was getting a higher reading compared to my gas gauge than before. I usually traveled 50 miles between the 1/4 markings on the gas gauge, winding up with about 190 miles with about an 1/8th tank of gas left when I refill it. I got to 212 miles with about an 1/8th tank left. When I filled the tank yesterday and made the MPG calculations from my last fill up, it seems that I was getting 18.34 MPG. I rarely put more than 11-12 gallons in the 15-7/8 gallon tank. This time, it was 11.595 gallons. Before the cover was installed, I was averaging around 16.5 MPG. The last time I filled up before the cover, I got 16.62 MPG. I haven't changed my driving habits despite the rising gas prices, or made any long trips, so it may be aerodynamics. The next time I fill up, the MPG will be calculated with having the cover on for the entire period between fill ups, so we'll see what develops. Watch the mpg drop and burst my balloon! :-)  SignatureBill In Hamptonburgh, NY To email, remove the double zeroes after @ > The beginning of this month I bought a soft tonneau cover for my 97 > Nissan PU, 2.4 l, 4 cyl FI, 62,500 miles. He's a good old boy and [quoted text clipped - 17 lines] > cover on for the entire period between fill ups, so we'll see what > develops. Watch the mpg drop and burst my balloon! :-) I've read that a bed cover does give better mileage. The tailgate acts as a spoiler with a lot of drag,so blocking the airflow into the truck bed reduces drag. SignatureJim Yanik jyanik at kua.net > The beginning of this month I bought a soft tonneau cover for my 97 > Nissan PU, 2.4 l, 4 cyl FI, 62,500 miles. He's a good old boy and looks [quoted text clipped - 18 lines] > develops. > Watch the mpg drop and burst my balloon! :-) Some mpg savings is to be expected. You have eliminated the rolling low pressure drag zone in the bed and created a boundary layer. The worst thing you can do is drive with the tailgate down, or off, or with one of those air gate things. However, to accurately determine the mpg, you will have to fill up the tank. "About" 1/8 tank is not good enough. Your gas gauge is not linear, either. >Some mpg savings is to be expected. >You have eliminated the rolling low pressure drag zone in the bed and [quoted text clipped - 3 lines] >However, to accurately determine the mpg, you will have to fill up the tank. >"About" 1/8 tank is not good enough. Your gas gauge is not linear, either. There are some detailed studies you can read on this... the cover would generally help, but you can get people to argue both sides. Depending on driving speeds, styles\, and conditions, you could find better results in a lot of different ways (same as other changes to a vehicle). Bottom line is that what counts is whether _your_ mileage improves. on 4/25/2008 8:13 PM Paul said the following: >> The beginning of this month I bought a soft tonneau cover for my 97 >> Nissan PU, 2.4 l, 4 cyl FI, 62,500 miles. He's a good old boy and [quoted text clipped - 29 lines] > "About" 1/8 tank is not good enough. Your gas gauge is not linear, > either. I 'fill up' when the gauge gets 'down' to about 1/8th of a tank, not just put 1/8ths of gas in the tank. SignatureBill In Hamptonburgh, NY To email, remove the double zeroes after @ who cares ! did you buy the cover for gas savings ? Dick > on 4/25/2008 8:13 PM Paul said the following: >>> The beginning of this month I bought a soft tonneau cover for my 97 [quoted text clipped - 32 lines] > I 'fill up' when the gauge gets 'down' to about 1/8th of a tank, not just > put 1/8ths of gas in the tank. on 4/26/2008 7:27 PM D. said the following: > who cares ! did you buy the cover for gas savings ? > Dick > Well, you care enough to comment. Dick is a good name for you. > >> on 4/25/2008 8:13 PM Paul said the following: [quoted text clipped - 38 lines] > > SignatureBill In Hamptonburgh, NY To email, remove the double zeroes after @ why don't you stick the cover in your a.s , a.shole !!!!!!! > on 4/26/2008 7:27 PM D. said the following: >> who cares ! did you buy the cover for gas savings ? [quoted text clipped - 40 lines] >>> I 'fill up' when the gauge gets 'down' to about 1/8th of a tank, not >>> just put 1/8ths of gas in the tank. > who cares ! did you buy the cover for gas savings ? > Dick [quoted text clipped - 33 lines] >> I 'fill up' when the gauge gets 'down' to about 1/8th of a tank, not just >> put 1/8ths of gas in the tank. I bought mine to cover the illegal aliens I employ........ Urban Legend This theory was disproved on Mythbusters an while back I'm glad your getting better mileage but I don't thing the cover is causing it > The beginning of this month I bought a soft tonneau cover for my 97 Nissan > PU, 2.4 l, 4 cyl FI, 62,500 miles. He's a good old boy and looks almost as [quoted text clipped - 17 lines] > on for the entire period between fill ups, so we'll see what develops. > Watch the mpg drop and burst my balloon! :-) > Urban Legend > > This theory was disproved on Mythbusters an while back Which theory? I love Mythbusters, but sometimes they don't think through their "proof." I think they did a good job with the tailgate up / tailgate down myth, but not so sure on the tonneau cover. As I recall, they showed no improvement for the tonneau for their particular vehicle and a maximum speed of 55 mph. I am not sure you can say this is generally true for all pick-ups and higher speeds. 55 mph is really not fast enough to make definitive statements about issues related to aerodynamic drag and fuel economy. It is in the range of the speed where aerodynamics becomes the primary influence on fuel economy (the actual transition point varies by vehicle). It is close enough to the transition point that other factors may still be primary, and mask the effects of aerodynamic improvements. I don't think comparing the mileage for one or two tankfuls of gas is going to prove anything in this case. The change in mileage is going to be small (probably on the order of a few percent at the most). Unless you have a lab set-up, you need to compare many miles of highway driving with and without the tonneau to come to a valid conclusion. A gas mileage log book would be essential to drawing a decent conclusion. Ed > I'm glad your getting better mileage but I don't thing the cover is > causing it [quoted text clipped - 22 lines] >> develops. >> Watch the mpg drop and burst my balloon! :-)
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