08-19-2013, 08:13 PM
DRR wrote:
[quote=Black]
I missed that DRR initially stated that downshifting increases fuel economy....
I never stated that. Downshifting as a matter of course for slowing decreases fuel economy by increasing engine RPM while in a lower gear, and keeping the injectors working. That increases your fuel consumption.
You didn't? What did you mean by:
DRR wrote:
As for downshifting instead of braking, just know that that puts additional stress on the motor, the transmission, and increases fuel economy
(Emphasis mine)
RAMd®d wrote:
but when I rent a newer manual car or when I drive my Dad's car. the fuel consumption goes to 0.0 (0 L per 100 Km) when downshifting.
I don't understand this.
With an automatic transmission, you take your foot of the gas pedal to use the brake pedal (normally). Butterflies close, acceleration goes to 0, but gas is fuel is still consumed, the rate of consumption decreasing as the rpm stabilize at idle.
Speedy wrote:
[quote=space-time]I believe on modern cars the injectors do not pump gas in cylinders in cases like these, this is why I see 99.9 MPG in some cars in USA (infinite gas mileage) and 0.0 L/km when driving in Europe (no gas consumption).
Always a little fuel going in to keep the engine running.
I will put my Diesel cars with auto trans into neutral as I approach a stop, then place in drive as I get close enough to let the high compression engines slow the cars nearly to a stop.
space-time has it correct. As mentioned by another poster above, most (all?) modern petrol cars cut fuel when the car is coasting and the RPMs are above a certain level. By putting the car in neutral, your car is actually consuming more fuel since it needs fuel to keep from stalling. Whereas when it's coasting it doesn't. I'm not sure if diesels do this or not.
Some newer cars even cut the engine at stoplights and start it back up when you push on the gas.