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July 12, 2012

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Jon

I think you should edit the paragraph that debunks fuel consumtion in neutral for clarity; it is misleading.

When in neutral, the same amount of fuel is being consumed whether you are rolling or stopped. The engine is disconnected from the final drive and it is left to spin only the torque converter and transmission input shaft.

When the vehicle is in gear, the situation is different. If you are DECELERATING with your foot off the gas pedal, the wheels are turning the transmission, and the trasmission is turning the engine, the opposite of acceleration. This means very little fuel is required to sustain RPM. As the vehicle comes to a stop (in gear still) the wheels stop rotating, but the engine is still turning. This is where the torque converter comes into play, it acts as a fluid coupling between the spinning engine crankshaft and fixed transmission input shaft. This fluid coupling imparts a resistive force on to the crank shaft, making the engine require slightly more fuel than if it were in neutral.

To summarize: the most fuel efficient way to drive an automatic is to leave it IN GEAR when decelerating, and to put it IN NEUTRAL when at a stop.

Petro-Canada

Thanks for the suggestion!
- The PumpTalk Team

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PumpTalk is a blog created by Petro-Canada, a Suncor business, to share information and engage in discussion about a number of topics, such as fuel efficiency and product responsibility. In our weekly posts, we discuss subjects that we believe are important and are of interest to drivers everywhere. Here you’ll find posts on gas prices, reducing fuel costs, sustainability, auto industry innovation, and vehicle safety and maintenance, as well as posts on climate change as it relates to the energy industry and our shared responsibility.

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