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I noticed something very interesting yesterday about my fuel mileage

Discussion in 'General Industry Discussions' started by Richard Martin, Apr 20, 2013.

  1. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    I took all of the equipment off of my trailer yesterday because I had to go and pick up some 12 foot long items for the house. Normally I get around 13 MPG with the equipment loaded up on the trailer. I figured that since I removed about 1800 pounds, give or take a few pounds, that my mileage would jump up to around 15 to 16 MPG. Boy was I surprised when the mileage actually dropped to 12.5 MPG.

    I think that even though the gate is made up of expanded metal, it is still acting like a big old sail and creating a lot of drag. When the mowers are on the trailer, it breaks up the wind and reduces the drag.

    I'm going to take the gates off of the trailer today and see if that makes a difference. If my mileage jumps up I'm going to try to make some sort of deflector to try and get the air up and over the equipment and tail gates on the trailer.

    The point of all of this is to try to get better gas mileage. Just switching from my 1995 F150 to this 2007 Chevy 1500 resulted in a 30% increase in fuel mileage. The Ford got 10 MPG and the Chevy is getting 13 MPG. I had seriously considered going to a 12 foot trailer with a single axle because of the reduced weight. But if weight is not the problem, then the tailgate must be.

    What do you guys think?
  2. Darryl G

    Darryl G LawnSite Fanatic
    Posts: 8,033

    I think your sampling is insufficient.
  3. CreativeLawncareSolutions

    CreativeLawncareSolutions LawnSite Silver Member
    Posts: 2,025

    The Mythbusters have already tested this. The conclusion...

    Closing the tailgate actually improves fuel efficiency because it creates a type of airflow called a separated bubble within the bed of the truck. As wind rushes over the moving truck, that bubble of slow-moving air deflects it over the raised tailgate. By guiding surrounding air over and across the bed of the truck, that vortex effect prevents added drag.

    However, driving with the tailgate open eliminates the bubble effect, pulling the air toward the truck bed and creating more drag rather than deflecting the wind. Some gas-conscious pickup drivers still swear by leaving their tailgates open, but science sides with leaving it up.
  4. sjessen

    sjessen LawnSite Gold Member
    Male, from Knoxville, Tn
    Posts: 3,319

    Richard, a number of years ago I had a small Toyota pickup for towing. Had to replace the gate on the trailer so went with one a foot taller with a finer mesh. Results were the truck was half a gear slower at highway speeds. So, yes the mesh gate makes a difference as does the weight of the tandem axle.

    You mileage is a good bit better than mine. I have a '03 F150 pulling a 14' tandem axle and get about 10 around town sometimes less. 13 mpg is really pretty good.
  5. Darryl G

    Darryl G LawnSite Fanatic
    Posts: 8,033

    A pickup truck bed and a trailer aren't exactly comparable.
  6. knox gsl

    knox gsl LawnSite Fanatic
    Posts: 5,054

    I would love to get 10 or 12.5 or 13 as of now I only get around 8.
    Posted via Mobile Device
  7. CreativeLawncareSolutions

    CreativeLawncareSolutions LawnSite Silver Member
    Posts: 2,025

    Yes, they are. It's the exact same concept...only bigger.

    He asked if it's the trailer gate that's doing it. It isn't. Science proved it.
  8. Darryl G

    Darryl G LawnSite Fanatic
    Posts: 8,033

    It's not the exact same thing....does your trailer have a cab? Does your truck have a 4 or 5 foot tall tailgate? Confounding variables!
    Last edited: Apr 20, 2013
  9. Snyder's Lawn Inc

    Snyder's Lawn Inc LawnSite Platinum Member
    Posts: 4,541

    You need to read better OP is talking about trailer tailgate not a pickup
    Stay on the subject on hand
  10. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    The tailgate on a pickup is a whole different scenario. The tailgate on the trailer cannot create a bubble because there are no sides on the trailer to contain the air pressure that creates the "bubble". The tailgate on a truck is also 8 feet behind the cab and lower than the cab. The tailgate on my trailer is 29 feet behind the cab of the truck.

    I know exactly what the bubble in the truck bed is. This is the same type of thing that happens with race cars when they draft. But just like with drafting, the closer the object is that is trying to draft, the greater the effect will be.

    This is easy to confirm. I'll just take the gates off of the trailer and see if the mileage increases. If it increases then the tailgate is causing drag. If it doesn't increase, then I continue to look for a 6 by 12 trailer.

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