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The difference b/t O/D and Power

483 Views 3 Replies 3 Participants Last post by  MNSpectraBlueIS
I have both on my car. I (well my dad at first) keep the O/D on. He tells me not to use power..cause wastes fuel. I only use it when having some fun. So whats the difference between overdrive and power? Sounds teh same to me...
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Overdrive shifts the gears at a lower RPM and doesn't wind them out as much. Power will wind each gear out at a higher RPM which will make the car take off faster.
What happens when u have both overdrive and power on? offset each other? So the way to go faster is Overdrive off and power on right? thanks.
The word 'overdrive' describes a gearing ratio that is higher than 1:1. For instance, most gears on the car have ratios like 3.5:1, 2:1, etc. On many vehicles the top gear (5th in the IS) is overdrive, with a ratio like 0.9:1 (that's just an example, I don't know the exact IS ratio).

Overdrive has nothing to do with shift patterns or varying RPMs at which gears shift. The Power button on the IS does vary the shift pattern/RPM. As far as I know, there is no 'overdrive off' switch on the IS. You could leave your car in 4th gear I suppose... On other vehicles with an O/D off switch, it is usually used when driving in hilly conditions or when pulling a trailer. Turning it off helps avoid repeated shifting up and down when the vehicle's highest gear isn't strong enough for the conditions. Running with O/D off will get you lower MPG because the engine is running constantly at a higher RPM (lower gear ratio). Running with the Power button on will probably get you lower MPG too because it tells the vehicle to shift down sooner in response to throttle changes.


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