It’s a common belief among drivers that shifting an automatic transmission car into neutral while idling — at a red light, in traffic, or during a brief stop — might save fuel. The logic sounds simple: if the car isn’t “in gear,” the engine must be working less, right?

But experiments and real-world observations suggest otherwise.

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What Happens in Drive vs. Neutral

In an automatic car, leaving the transmission in Drive (D) at a standstill engages the torque converter, lightly loading the engine. Shift into Neutral (N), and that load disappears. At first glance, it might seem like removing that small resistance would reduce fuel consumption.

However, what actually happens is counterintuitive:

• In Drive, the engine control unit (ECU) keeps the idle speed steady, typically around 650–750 RPM.
• In Neutral, many cars slightly raise the idle speed — for smoother re-engagement and stability — pushing the RPMs a bit higher.

That higher idle speed means the engine burns more fuel, not less, even though it isn’t “pushing against” the transmission.

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The Experiment

In a controlled test, drivers measured the fuel flow while idling in both Drive and Neutral. The findings:

• In Neutral → the RPM increased slightly, resulting in more fuel being consumed.
• In Drive → the RPM stayed at its baseline, with lower fuel burn overall.

The difference might be small per stop, but over time, it adds up. Instead of saving fuel, idling in Neutral can actually increase your fuel consumption.

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What About Wear and Tear?

Some people argue that shifting into Neutral reduces strain on the transmission. In reality, modern automatics are designed to idle in Drive without harm. Constantly shifting between Drive and Neutral can actually cause unnecessary wear on the transmission linkage.

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The Bottom Line

For automatic transmission cars:

• Idling in Neutral does not save fuel.
• In many cases, it can cause the engine to run slightly faster, burning more fuel.
• It also adds extra, unnecessary shifting that doesn’t benefit your car.

The best practice? Leave the car in Drive when waiting at lights or in traffic. If the stop will be long (like at a railway crossing), putting the car in Park or turning off the engine entirely is more fuel-efficient and mechanically sensible.

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✅ Conclusion: The old “Neutral saves gas” myth doesn’t hold up. With modern automatic cars, you’re better off just leaving it in Drive.