Fuel economy - Throttle VS. Gears?

Question

I've always wondered, cause I need to save petrol due to the rising prices... :P Say I'm driving along in my car, and start going up a hill, the car slows down, am I better to open the throttle further or change down gears?

What the real question is, if you didn't quite get that, is, which uses more fuel? More open throttle or higher rpm (from changing down a gear)?

My friend says you can floor the car and it won't use much more fuel, because the RPM dictate how much fuel is injected, but I'm not sure whether to believe him or not. The sound of the car changes a lot from say 40% throttle to 100%, which makes me think it's getting a lot more fuel.

Answer 1

Throttle, Top Gear proves this in the esp 1 season 6.

M3 vs Prius. and the M3 won.

Answer 2

well normally going uphill will slow down the car for sure,  and i say change the gear so as not to stall the car. it will cost you more fuel if you stop and start trekking  midway uphill..

Answer 3

When you car is under heavy load, the engine computer runs the car rich (extra fuel) so it does use more fuel - even at the same RPM.

When you are climbing a hill, forget about the gas mileage.  Keep the engine from stalling.  That is your number one concern (and for safety).  

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Also, it is BETTER (for the life of the engine) to rev it higher than to stress it out by floor the gas pedal (assuming the car has good lubrication).  Any money you save (very little) by not down shifting might be wasted on engine repair later on.

Good Luck...

Answer 4

I lower the gear one, plus if you force the car to much you'll blow it