Gas mileage

Wingnut · May 23, 2004

So...I decide to head down to Dallas for the weekend, and decide to do an experiment on gas mileage.

On the way down, it was in the mid 80s, and I kept the truck between 75 and 80 the entire way.

14.8 miles per gallon. About par for the course.

On the way back today, it was about 95 degrees out, so I had the AC on. I bit the bullet, and set the cruise at 65 mph for the entire trip home.

I got 21.2 miles per gallon. WITH THE AC ON!

Amazing. I'm quite impressed.

I'm no longer a doubter of those with claims of high teens MPGs. They just drive like grannys.

asepgrad98 · May 23, 2004

once you get over 45mph or so turning on the AC actually HELPS mpg due to less drag of windows up. Glad to hear you hit 20's

Wingnut · May 23, 2004

Winders were up and AC was on for the trip down too. Forgot to mention that.

redvett · May 24, 2004

The best aerodynamics is windows up all the time and A/C on only when it gets too hot. Windows open and tailgate down are a drag on fuel mileage.

Draphty · May 24, 2004

Hey wingnut...I'm in Keller, Tx about 15 miles Northeast of Ft. Worth....Playing a big part in your crappy mileage coming this way was the stiff winds out of the south that we've had lately. That can greatly effect your mileage.

Chuckster · May 24, 2004

So...I decide to head down to Dallas for the weekend, and decide to do an experiment on gas mileage.

On the way down, it was in the mid 80s, and I kept the truck between 75 and 80 the entire way.

14.8 miles per gallon. About par for the course.

On the way back today, it was about 95 degrees out, so I had the AC on. I bit the bullet, and set the cruise at 65 mph for the entire trip home.

I got 21.2 miles per gallon. WITH THE AC ON!

Amazing. I'm quite impressed.

I'm no longer a doubter of those with claims of high teens MPGs. They just drive like grannys.

At 75mph, I get exactly 17.5mpg in a 5.3l Tahoe with 3:73's

I cannot drive any slower than that....

Wingnut · May 24, 2004

Hey wingnut...I'm in Keller, Tx about 15 miles Northeast of Ft. Worth....Playing a big part in your crappy mileage coming this way was the stiff winds out of the south that we've had lately. That can greatly effect your mileage.

Yup, I know that...But I usually get only 13-14 mpg anyway. So the 14.8 was pretty darn good for me. Going better than 20....Well...That's just......

black&grayHD · May 24, 2004

MSUChevyMan · May 24, 2004

Hey REDVETT, how does tailgate down reduce aerodynamics and affect gas mileage negatively? I've always thought it to be the other way...

Wingnut · May 24, 2004

I only had one truck that dropping the tailgate helped gas mileage, and that was a long bed, and it only helped about 1/2 mpg.

Every other truck I've owned it hasn't made a bit of difference.

SteveCZ · May 24, 2004

I have to agree with WingNut,

Motor Trend took a truck (forget which make / model) for a trip from LA to Texas I beleive and back.

They drove one way with the tail gate up, the other with it down, and didn't notice enough difference to comment about.

Go figure

I'm still glad I have my Tonneau cover though..

Blue-2001-Z71 · May 24, 2004

I drove 700 miles with the gate up and 700 with it down. I actually LOST 1/2 MPG with the gate down, so it didn't do me a bit of good. Justas well, I hate driving with a heavy steel panel free to bounce around as I hit bumps. Looks better up too (and looks add HP!)

ness5575 · May 24, 2004

i saw a report a few years back (dont remember where anymore) where they compared the mpg of driving with the tailgate down vs up. up was better because the areodynamics are designed for the tailgate to be up, and when it was down the areodynamics decreased, and thus decreased gas mileage.

sinces these gas prices have spiked, I have been making an effort to drive more economicaly. going 5 over instead of the normal 10 on the freeway, no full throttle acceleration on on ramps, etc. that has increased my mpg from 15 on average to 17. not sure how long i will be able to keep that up, buti found it interesting...

redvett · May 24, 2004

Hey REDVETT, how does tailgate down reduce aerodynamics and affect gas mileage negatively? I've always thought it to be the other way...

I worked for GM truck (engineering now retired) on the electric truck i was at the wind tunnel and saw for myself the effects of tailgate up & down and with a tonneau cover. When tailgate is down there is a vacuum created under the vehicle which decreases mileage & with it up there is an air bubble in the box and it actually cuts drag. When even the rear half of the box was covered it helped mileage. I have tried various things and checked mileage on my 140 mile trip up north with steady x-way driving and it works to the effect a tonneau helps 1 mpg.

I am getting a report soon and will post it here. Was written by an automotive mag.