Can A Car's Gas Mileage Be Improved By Adding Golf Ball Dimples?

Posted by Minnesotastan in Car & Vehicle on October 23, 2009 at 12:28 pm


car with dimplesIt has been argued that dirty cars are more fuel efficient than clean ones for the same reason that dimples on a golf ball improve its aerodynamics during flight.  The team at Mythbusters tested these hypotheses and found that a dirty car did NOT achieve improved gas mileage, BUT…

For a full-scale test, Adam and Jamie put a layer of clay on a car and did two more sets of runs on their track – one with a smooth clay surface, the other with dimples pressed into it. The respective fuel efficiencies were calculated as 26 and 29 miles per gallon. Although the original myth was invalid, the theory behind it was sound, leading to a final judgment of “Busted, Concept Plausible”.

Discussion threads on several auto forums discussing the Mythbusters episode note that “shark skin” textures on military fighter aircraft (and on America’s Cup yachts) serve the same purpose, that dimpling on the undercarriage of some Lexus cars reduces noise (by reducing friction), and that textured paint is banned on professional race cars.

Mythbusters achieved the dimpled effect using modeling clay applied to the surface of a Ford Taurus.  It’s not clear whether the same effect could be achieved with a ball-peen hammer.

Screencap credit.  A brief YouTube video of the car (not the full episode) is here.


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16 comments to "Can A Car's Gas Mileage Be Improved By Adding Golf Ball Dimples?"

  1. Dr. Detroit
    October 23rd, 2009 at 12:48 pm

    Argsh... Let's hammer Detroit!!

  2. GeekMan
    October 23rd, 2009 at 12:51 pm

    If you're creating the dimples by adding a layer of clay, then doesn't the dimpled car have less clay, weigh less, and hence use less gas?

  3. Minnesotastan
    October 23rd, 2009 at 1:04 pm

    @Geekman - the weight of the car didn't affect mileage at a constant speed (it might have an effect during acceleration or on upgrades). In any case, Mythbusters controlled for this by taking the clay removed in the dimpling process and putting it in the back seat of the car, so that the dimpled car weighed the same as the undimpled control.

  4. Splint Chesthair
    October 23rd, 2009 at 1:12 pm

    Simpsons did it!

    Ned: Whatcha diddely-doin', neighbor?
    Homer: Aw, putting speed holes in my car. Makes it go faster.

  5. Tracie
    October 23rd, 2009 at 1:26 pm

    My Ford Taurus was caught in a hailstorm a few years, creating several small dimples... you think those will help?

  6. b0rsuk
    October 23rd, 2009 at 2:40 pm

    Based on an article I've read a while ago, I say this is to milk naive people out of their money. It compares golf balls to airplane wings and describes why dimples are not good for an airplane wing. Long story short, there's no perfect aerodynamic surface. It depends on object's shape. Have a look:

    http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml

  7. Skipweasel
    October 23rd, 2009 at 3:12 pm

    A good hailstorm ought to fix it.

  8. Manticore
    October 24th, 2009 at 1:06 am

    they mention something about it not working by just hammering dents in the metal before they started putting clay on the car. I don't remember exactly what they said but yea.

  9. BikerRay
    October 24th, 2009 at 6:11 am

    Minnesotastan - If the weight didn't affect mileage, they're doing it wrong. Weight lowers mileage because it flattens the tires, increasing drag (same for bearing drag).
    They should have used a wind tunnel. But then, I'm sure the manufacturers have done that already.

  10. Zero
    October 24th, 2009 at 6:25 am

    A textured surface will have lower drag, and therefor, be more efficient, than a smooth surface, all else being equal. It would take some research to determine the right texture, but it could be done. However, most people seem to be forgetting that the myth was that a normal dirty car would get better MPG due to a dimple-like effect. The chances of normal dirt, dust, mud, and other road grime just happening to provide this effect are virtually non-existent. If the real world, the highly irregular pattern will add parasitic drag and lower fuel efficiency. Even if (or more likely, when) textured surfaces become common, dirt will affect MPG even more in the wrong direction.

  11. Bonnie L.
    October 24th, 2009 at 12:35 pm

    Biker Ray-
    They did the experiment over the course of one mile and the car was already up to speed at the start of that mile. Meaning that the long term affects of the extra weight were not part of the results. They even stated that the extra weight of the clay would, indeed, eventually cause a negative impact on fuel efficiency and that the cost of fuel to get the car up to speed were equally negative.

    However, the point of the experiment was to see if the evenly dimpled surface would have a "golf ball-like affect" and decrease the drag and fuel consumption. Since metal doesn't easily form uniform dimples, they were forced to coat the car in clay and dimple the clay. All of the experiments were carried out on the same course and at the same speed, meaning that the per mile fuel consumption can be compared and a fairly accurate conclusion can be reached.

  12. Yani365
    October 25th, 2009 at 10:03 pm

    The reason golf balls have dimples is for control and for longer distance due to INTERACTION with the air.

    Specifically, the dimples create drag due to a delayed separation layer, and hence less turbulence behind the ball. (some studies say the turbulence is made smaller, and is thus reduced.)

    The reduction of turbulence adds to the distance traveled. (there are other control effects of dimples not relevant to the car application.)

    The car only deals with separation at the rear of the roof and the rear of the trunk lid. The rest of the dimples are only causing pure drag.

  13. John Simms
    October 29th, 2009 at 6:27 am

    I saw the episode last night. It was obvious the dimpled care got better fuel economy. So much so that car manufacturers should start making cars resemble golf balls.

  14. WIDTAP
    October 29th, 2009 at 1:32 pm

    It’s not clear whether the same effect could be achieved with a ball-peen hammer.

    This is an experiment reserved for the recently divorced with a sports car.

  15. Scott Mitchell
    October 30th, 2009 at 9:52 am

    I saw the Mythbusters golf ball car episode. Very cool. I think dimples may be the key to better MPGs, but there may be other ways to focus the benefit with not necessarily dimples but other indentions, or bumps and vallys on a cars surface. It is obvious that dimples boosted MPGs by 11%, what if we could get that number to 20% or 30% or more. To the the Wind-Tunnels!

  16. orange leader
    October 30th, 2009 at 10:20 pm

    Just so you know,(and don't try it yourself), I tried to sell a do-it-yourself gas mileage improvement/dimple kit a year ago on Minneapolis craigslist, auto section. $50 for a ball-peen hammer. I posted pictures of the golf ball and it's aerodynamics, and the choice tool, and of a hail damaged car. Yes I meant it as a joke, but someone must have thought I was serious, because the ad was flagged and removed within about 10 minutes.

    Nice to know my hypothesis had merit though.


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