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Do you use any gas at all if you take your foot off the gas pedal and just coast? I was thinking of this the other day.....

 
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I dont think so, the momentum of your speed keeps you coasting. when you take your foot off the gas you dont use gas.

 
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combustion engines need gas to operate, so as long as you have your engine turned on it will be using gas, not as much as if you were mashin the pedal though (increase rpm = increase gas usage)

 
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of corse you use gas the engine is still turning. witch means the fule pump is still putting fule to the engine at any point the engine is on.

 
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If you let your foot off the gas it closes the throttle plate, but then the ECU itself controls how much air gets past the throttle plate by opening and closing the IAC valve (Idle Air Control). It basically compensates for engine load while idling. If your A/C is on it'll raise the rpm's slighty for example.

 
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Okay, Mohawkboom said your injectors turn off when you take your foot off the gas in an earlier post...

 
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The injectors "turn off" when the key is out of the iginition or when the rpm's drop below a certain number to cause the starter motor to crank the engine.

 
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I see.. so if your coasting, and the downshift effect is turning the engine, then why does it need extra "help" (fuel) to turn the motor? Doesnt the wheels turn it alone? (while off the gas)

 
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I guess it doesn't, but if you're going downhill and you let off the gas and you take it out of gear (neutral), then the rpm's are at idle. That means the engine is still getting some fuel. Now, if you turn the ignition off. Then the rpm's fall to 0 and you don't get any fuel. Now try putting the engine in gear. It'll make the rpm's shoot up.

 
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the engine needs gas at all times, providing it has been ignited which happens when you turn the key, the spark plugs fire in a sequence and with that spark is a spurt of fuel, which combusts or explodes in the cylinder and causes the piston to move which in turn gives you your engine power even when your foot is on the gas, so basicly if you turn your car on, set it in your driveway and dont' drive it, or just let it roll down a hill, about a 500mile long hill with no stops or turns or intersections, it will eventually run out of gas.[IMG]i/expressions/face-icon-small-tongue.gif[/IMG]