I’m assuming it’s the overdrive button on the side of my gearshift. 2012 Nissan Altima, base model. Everything I googled assumes I know more than how to change oil. Thanks in advance!!! 😊
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Overdrive is essentially another gear ratio. All it does is reduce the ratio between the input shaft of the transmission, and the output shaft. If you had a transmission with four gears, the highest gear (lowest ratio) would mean that for every turn of the engine, you would get perhaps .8 turns of the wheel. An overdrive gear might make that 1 or 1.2 turns of the wheel for every turn of the engine.
This means that for the same engine speed (RPM), the wheels would turn more often, which means you could maintain the same speed, but the engine would run slower, meaning you could travel at highway speeds with lower fuel consumption. The tradeoff as always, is that you have less mechanical advantage to accelerate if the need arises.
It’s precisely the same thing as gears on a bicycle. The higher the gear, the harder it is to pedal, but the slower you need to pedal. Think of overdrive as just adding another higher gear on your bike.
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