The MythBusters The MythBusters

MythBusters Episode 127: Dirty vs. Clean Car

Premier Date: October 21, 2009

A dirty car is more fuel efficient than a clean car because the dirt makes the car more aerodynamic like the dimples on a golf ball.

busted (concept plausible)

Adam and Jamie covered a car in dirt and mud and drove it down a track at highway speeds to measure its fuel efficiency, and repeated the test after the car was cleaned. They discovered that the average gas mileage for the dirty car was 24 miles per gallon while the clean car performed better at 26 miles per gallon. They then tested the reasoning behind the myth, and tested how well dimpled golf balls performed against smooth balls. They discovered that dimpled golf balls could fly almost twice as far as smooth balls. Dimpled balls disrupt the air around them, creating a smaller wake behind them and reducing drag. 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”.

A hangover caused by beer is less severe than one caused by a mixture of beer and liquor.


To perform this test, Tory and Grant would have to eat the same food, drink their alcohol at the same time, and sleep for the same length of time in the warehouse for consistent results. Kari (who could not take part because of her pregnancy) then devised a battery of tests to measure dehydration, memory, light/sound/motion sensitivity, and coordination. Without having drunk alcohol, Tory and Grant performed well on their control test. They then performed the beer test, with Tory drinking 14 cans of beer and Grant drinking six. They both performed significantly worse than the control tests, signifying they were badly hung over. They then repeated the test with a mixture of beer and liquor, making sure to drink an equivalent amount of alcohol as in the first test. The next morning, Tory and Grant improved significantly and felt much better than in the previous test. Thus, the Build Team declared the myth busted.