Popular Science experiment yields 26.0mpg from DMAX

[DMAXDiva]

There's an interesting article in August's Popular Science magazine regarding an experiment proving that "pickups and SUV's don't have to guzzle fuel"...Hypothesis: "When it comes to gas mileage, it's not only what you drive but how you drive."

Two vehicles, a 2500HD Silverado CC DMAX (tranny wasn't mentioned, nor was 4wd option mentioned) and a Mercury Sable w/3.0 V6 were driven over 195 miles of interstate. The DMAX's cruise was set at 55mph, the Sable was driven "normally" (hard acceleration, full-throttle passing). Aerodynamics of the truck had been improved by covering the bed with plastic sheeting (ala tonneau cover), taping across the grille to improve airflow around truck, and blocking the gap between body and frame rails.

Results: "Success! The Silverado clocked 26.0 mpg during our experiment, while the Sable got only 24.6 mpg...and though it burned less fuel and created less carbon dioxide, the Silverado did belch more nitrogen oxides and soot. Nevertheless, it's an impressive win for big trucks. Hypothesis proven."

Okay, having just copied all that from the article, I can personally interject that on a 1200 mile round trip I took this past week, my truck's best highway mpg was only 17.3...and no, I won't be stretching plastic sheeting across the bed, or taping across the grille, or anything else PopSci mentioned...I'm still pretty darned happy with the mileage, considering the fact that cruise was set at 85mph w/ AC a blowin' and Juice a flowin'...I do love this truck! :D :D :D

[SoCalDMAX]

I also read that article. Although I'm very encouraged that they did hit 26.0mpg, they did skew it as far as possible with 55mph driving, the aerodymanic stuff and driving the car kinda hard.

I've got a bed cover, can't say for sure if it's helping much. I'll probably try the underbody aerodynamics, since I have full running boards and it could be attached to the brackets. I don't think there's any way one could tape off that much of the grill area and not affect cooling, especially towing in the summer.

I wonder how they decided which brand of diesel truck to use for the test....

Regards, Steve

[NutNbutGMC]

QUOTE:
considering the fact that cruise was set at 85mph w/ AC a blowin' and Juice a flowin'..
__________________________________________________ _________________

Ya' gotta' love this woman. smile.gif 85 mph, chillin' and juiced for action... :D

DMAXDiva <===== speed, and performance... Who's your sister? Whoooo's your sister?

[ 08-11-2002: Message edited by: NutNbutGMC ]</p>

[bora]

I have a long trip coming up next weekend, I am looking forward to seeing what the mileage is going to be. I do have a camper shell so I expect to see some aero benefits from it. This will be our first trip not towing, we usually tow our race car trailer and get anywhere between 13 to 10 mpg depending on the headwinds.

Sometimes I wish I sprang for the V-nose trailer instead of the aero wedge shape of the Elite II.

Anyone think the nose cone may help with
the aero of the trailer.

[moisheh]

Bora: Camper shells are reputed to reduce gas mileage. Socal dmax: My fleet salesman says that when he was at a GM do in Arizona the engineers told him that running boards will take 1 to 1.5 mpg away. SO I have a camper shell and running boards and lousy mileage. Seriously I have notriced a slight improvement without the shell.

[BobNelson]

17.5 is not bad... My 3500 only gets about that on the open road at 70-75. Since day one, I have an overall average of 15.3 at 25,000 miles now. A bunch of that is with 4k lb plus load.

Seems like your 2500 should do a little better, or ya just gotta get ur ft outa it...

No complaints from the hinterlands.. ;)

[bora]

I find it hard to believe that the camper shells will reduce gas mileage.

It should be better than the aero-brake lift-gate constantly dragging the rear.

My camper shell is flush with the roof of the truck and has a nice smooth rear side.

It would be interesting to try these out in a wind tunnel and see what Cd they come out at.

Does anyone have a wind tunnel that we can use.

[SoCalDMAX]

moisheh,

I don't doubt that running boards decrease mileage some. Perhaps doing the flat panels might help a little...

bora,

I saw a link to a wind tunnel test done at a university, it was kinda surprising. The best results were on a truck with a sloping camper shell, started out cab height and sloped down to the tailgate. IIRC, the second best was a bed cover, then tailgate up (surprise!) then tailgate down and finally a traditional camper shell. The tailgate up wasn't that disruptive, not too much air hit it, but tailgate down messed with the upper and lower air streams.

The difference between best to worst was not that much, perhaps 5% or so. The front aerodynamics probably play a much bigger role in the big picture.

Regards, Steve

[Diesel Dan]

Those older style aluminum toppers have to create more drag with all the exposed braces. One lady at work lost some MPG when she installed her aluminum topper vs the open bed and no topper. I work with many people that drive 50+ miles aday and consenses is tonneau(sp?) covers increase mpg.

[AlaskaDmax]

I have been running some distances over the last month...340 round trip, several times and achieved 19.6 MPG last week and 18.6 MPG this week. That is running between 50 MPH and 95 MPH...some city driving as well. The highway speeds are all through Alaskan mountain terrain, open bed, no body mods and all bare *ss, balls to the wall.

side note:
Seen you a few times up in the hills there Maverick...been waving at ya as I fly by but figured you wouldn't see anything but the big white blur!!!! :D :D :D :D :D