Today: one of the simplest ways to save on gas.

Dear Car Talk

Dear Car Talk | Jul 01, 2008

Dear Tom and Ray:

This is a question I have always thought I knew the answer to, but now I am searching for a concrete answer, and who better to turn to? Does a vehicle use more gasoline in starting the engine than it uses in idling for say, five to 10 minutes? The reason for the question comes from "discussions" with my wife about why I leave the car running when I run into the local 7-11. With gas prices being in the headlines on a daily basis now, she says it's a waste of gas to leave the car running, while I debate that the car burns more gas during ignition. Therefore, more-frequent shutoffs equal more burned gas. Being the husband, I am told by my wife that I am always wrong. Any chance I'm right this time? -- Charlie

TOM: Well, Charlie, good news: Your record is perfect. You're wrong again!

RAY: The only vehicle I know of that uses a ton of extra fuel getting started is the space shuttle.

TOM: All modern cars have computer-controlled fuel-injection systems, which meter out precisely the amount of gasoline the engine needs, and no more.

RAY: So, starting the car uses no additional gasoline. Your wife is absolutely right that if you're running into a convenience store, you should definitely turn off the engine to save fuel.

TOM: Hybrid vehicles do this automatically. When you come to a stop at a traffic light, even for a few seconds, the engine automatically shuts down. And then, as soon as you touch the gas pedal, it starts right up seamlessly, and takes you on your way.

RAY: And pretty soon, I suspect, lots of nonhybrid cars are going to have that same "stop-start" technology, because it DOES save quite a bit of fuel.

TOM: If it makes being wrong again any easier to take, Charlie, we should tell you that there was a time when cars had horribly wasteful carburetors. In those days, there probably WAS enough fuel leaking down and percolating to have made you correct -- if you were driving a '67 Buick Special.

RAY: And since you've obviously held this opinion for years, I don't see any reason for you to admit to your wife that you're wrong. Just tell her that the facts have had the audacity to change while you weren't paying attention.

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