Quote:

Huh ? Fuel is burnt accordingly to how many rpm.



Absolutely incorrect. While RPM can be a very rough estimate of consumption on an ATX, it means nothing on MTX.

When an Engine turns the transmission it uses gas. When the transmission turns the engine, there is no (actually very little) gas consumption. There is just enough to produce compression rather than combustion.

If I go 60 in 5th, I'm at 2500rpm. If I let off the gas, the fuel cuts off from the engine (largely), but I'm still going 2500rpm. I'm using the same amount of gas as I would be if I pressed in the clutch, sending the RPMs down to 750. The Tach means nothing for gas consumption, as I'm using the same gas at 750 with the engine decoupled from the drivetrain as I am at 2500 with the engine coupled to it.

If I downshift to 4th it'll go to 4000 -- I'm still not burning (much) fuel. The RPMs are higher, but that's just the transmission revving the engine, not the engine revving the transmission. I'm still burning roughly the same amount of gas I would be at 750rpm even though I'm at 4000.

You could downshift from 5th to 3rd, blow the [censored] out of the RPMs, and still not use much gas. Until you tried to actually put power to the wheels that is -- then you'd have to hit 6,000RPMs just to get somewhere -- then you would use more gas.

Downshifting doesn't use gas -- driving in the lower gear will use gas. But that's moot since we're talking about stopping your car, so you wouldn't be giving it any gas unless you needed to move in an emergency, in which case you're going to be glad you're in that lower gear.


2003 Mazda6s 3.0L MTX Webpage 2004 Mazda3s 2.3L ATX