MythBusters: Clean Car vs Dirty Car

by Reece @ DI

Adam and Jamie of the MythBusters crew get down and dirty with the myth that a dirty car gets better gas mileage than a clean car. Now before you say anything I know what you are thinking, how could this be true? I mean it goes against everything us detailers and car enthusiasts believe. A dirty car getting better gas mileage than a sparkly clean imperfection free vehicle!? No way! But not so fast, Adam and Jamie come across some interesting conclusions. During 5 trips at 65 mph with the same car, a dirty car achieved 24 mpg, while a clean car reached 26.4 mpg. This clearly shows that a clean car certainly gets better gas mileage than a dirty car. However, what if you incorporate the golf ball effect to the dirty car?

Golf balls are known for their dimples, but what if a golf ball was smooth like the clean car. The Mythbusters guys headed to the driving range and after some testing the numbers were astonishing. The golf balls without dimples traveled an average of 556 ft, while the golf balls with dimples traveled an amazing 893 ft. That is a 37% improvement!

The key here is that the dimples help with the wind drag on the ball. The clean ball has a 8.5 inch air pocket behind the ball that helps slow it down, causing it to go a lot shorter in comparison to the dimpled ball, which only has a 6 inch air pocket behind it. After seeing this it is only natural, apply this concept to the car!

Using clay Adam and Jamie create a smooth layer over the same car used earlier. After the same tests this car achieved 26 mpg, pretty much spot on as the clean car measured. They then took this same car and created golf ball like dimples across the entire vehicle, while running it through the same exact tests. They found that the dimpled car achieved 29.65 mpg, an 11% improvement!

It looks like the myth of a dirty car getting more gas mileage than a clean car was clearly busted, however with golf ball technology a dirty car is certainly more efficient.

Take a look at the videos below to see the entire episode in detail!