Popular Mechanics put frequently shared fuel-saving advice to the test by outfitting an ordinary ten-year-old car with an extremely accurate fuel economy gauge and trying all the gas-saving driving tactics they could think of. The results from three of the tests are listed below in this abridged version of the original article.

Tactic No. 1: Coast to a Stop - While brakes are necessary, they're inherently wasteful: They take the kinetic energy of a moving car - energy it took pricey gasoline to generate - and turn it into heat that's lost to the air. Everyone knows that accelerating until the last moment then braking hard to stop is less efficient than slowly coasting to a red light. But Popular Mechanics’ test data proves that coasting to a stop boosted fuel efficiency more than 50%. The lesson: Anticipate that a light will turn red and ease off the gas. Generally, the less you brake, the better your fuel economy.

Tactic No. 2: Avoid Slowly Crawling Up to Speed - Conventional wisdom says that jackrabbit starts consume more fuel. But it turns out that nursing your speed up to the limit too slowly also lowers mpg. Cars get poorer fuel economy in lower gears, and accelerating too slowly prevents up-shifting at an efficient rate. The best acceleration rate varies with the vehicle, gear ratios and weight, but Popular Mechanics testing found that taking 15 seconds to accelerate to 50 mph used less fuel than taking 30 seconds to reach the same speed because the car entered its top, fuel-saving gear sooner.

Tactic No. 3: Close the Windows and Use the A/C at High Speeds - It's a fierce efficiency debate: Should you open the windows in summer to avoid running your energy-intensive air conditioner, or keep the windows closed and the A/C on to preserve your car's aerodynamic profile. Popular Mechanics’ testing settled the issue. Driving at 55 mph with the A/C running, the test car got 24 mpg; turning it off bumped it up to 28 mpg. Then, as all four windows were opened one at a time, 1 mpg was lost each time another window was opened until the mileage was back down to 24 mpg. So, at 55 miles per hour, it's a wash. But aerodynamic drag rises exponentially with speed; the faster you go, the more the open windows hurt efficiency. The answer? Below 55 mph, open the windows and leave the A/C off. But at 60 mph or higher, keep them closed and the air conditioning running to burn less fuel.

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