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      01-14-2013, 01:57 AM   #6
E60 to E90 to E92
Roleez's Avatar

Drives: 2011 E92 335i M-Sport 6MT
Join Date: Sep 2009
Location: NorCal

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Originally Posted by avol3xo View Post
coasting down a hill I just put it in N so it saves gas
Coming up to a light, N makes sense. I do this in the last 100 feet before a stop, but never like half a block or more before stopping. But sorry, coasting down a hill in normal driving DOESN'T save gas in N. Do people driving automatics constantly place the gearshift in N coasting down a hill, let alone coming up to a stop? Never heard of it.

Think about it ... when in gear (regardless of transmission) going down a hill, letting off the throttle *shuts off* fuel injection, therefore no fuel is being burned. If fuel injection is stopped, car slows down because no fuel is consumed. Placing a car in N while at speed still burns fuel because you are placing the car at idle. How is idle maintained? By *burning fuel* to keep the engine running! Sure the car will coast in N, but you're just burning fuel with that unnecessary, improper practice. I (as I'm sure the majority of MT drivers) let up on the throttle to coast. Zero fuel consumed until I get back on the throttle.

Proof? If your car has an instantaneous mpg gauge, watch the readout in N at speed vs. letting off the throttle at speed while still in gear. Readout in N at speed will still continue to show a reading, meaning fuel is still being consumed for the engine to maintain idle. Letting off the throttle at speed in gear, mpg readout will have no reading (or infinitesimal, i.e. 99+ mpg), meaning ZERO fuel consumption.
2011 E92 335i 6MT (Space Gray/Coral): M-Sport / Premium / Convenience / Navi / L7 / InvisiGuard / Dinan Exhaust & Pedals
2011 CR-Z EX 6MT, 2008 GSX-R600
RETIRED: 2008 Dinan M5 SMG, 2006 330i 6MT, 2006 Dinan 550i 6MT, 1992 Accord EX 5MT