Gas mileage. When you run the same speed at a lower rpm, then you can save gas.
it´s clear that the ligher you go on the gas pedal, the more gas you save, although if you are going downhill and you engage a gear tat keeps the engine runing without using the gas pedal, ther is virtually no aditional gas consumpition.
While this is not necessarily recommended, disabling overdrive can also give you a bit of a extra kick when climbing hills or passing. 4 cylinder engines are notorious for lacking torque, which is what gets you going from low RPM. However, 4 cylinder's typically can rev much higher than larger engines, like V6s or V8s. The higher RPMs is where a 4 cylinder engine produces most of it's power. The overdrive "gear" is there to reduce fuel consumption, this is true. But if you turn this "gear" off while climbing a steep grade or while attempting to pass, you circumvent the Corolla's tendency to lag due to the transmission hesitating to kick down a gear. You also overcome the lack of torque the engine is capable of putting out by taking the car up into the higher RPM range where Horsepower takes over. In emergency maneuvers, an overdrive switch can also help you by using the engine as another form of braking. For instance, if you need to slow down rapidly while tapping into immediate power to avoid an accident happening in front of you, your overdrive switch is your friend. Another example is if you are on a very long downhill grade and your breaks start to overheat (not common unless you use cheap parts). If you find your brakes are beginning to become very spongy and the car is not responding to them, you can disable the overdrive and allow the engine's rev-limiter slow the acceleration of the vehicle. CAUTION: Using your overdrive switch in such ways can, and with repeated use, will damage your vehicle. However, if your choice is failing to avoid an accident or not having enough power to pull a small U-hall up a 5% grade, using your overdrive switch can be very helpful.
Overdrive in most automatic 4-gear transmission, just allows the transmaission to access the 4th gear. when in Drive, it locks out the 4th gear. You will always go faster quicker NOT using overdrive You will always go further WITH overdrive as it's a fuel daving Highway gear. And if you tow, turn your overdrive off. I've heard it can damage your trnasmission towing in overdrive. as for hills, climbing and decending, thats what the 1&2 gears are on there for. they activate the engine brakes so you don't wear your breaks down due to continuous excessive use. Always come to a complete stop before switching into these gears.
You normally leave 'overdrive' on, unless you want extra pulling power up a hill, or engine braking power down a hill.
do not use OD in stop and go traffic,climeing hills or in snow or ice it heats up the tranny,OD is meant to be used on long trips to keep engine rpm,s lower and help on gas mpg.
it makes the car run on higher rpm with less gas mileage..use it for long trips or when cruise control is on.. dont use it for emergency braking and situations like it because it will blow your engine and f*ck up your transmission...uphill climbs are more on lower gears than using OD because it will cause slippage or over-rev if the hill is too steep and you'll just make the engine work harder with more hp but lesser traction.
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