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Old 01-25-2013, 04:06 AM
d geek d geek is offline
diesel evangelist
Location: San Antonio, TX, USA
 
Join Date: Nov 2008
Posts: 2,058
Mein Auto: Camry hybrid + MB e300D-T
Quote:
Originally Posted by Taeksoo View Post
I'm no engineer (obviously) but just wanted to ask if this is right.
I noticed when I'm in Drive and braking my rpm goes down then up and then down then up.
It seems like it's down shifting while stopping.
I would have thought that this would waste more gas.
I'm just curious if anyone can explain why this is and why it would be more gas efficient? Or it's not gas efficient but help stop faster?

Sent from my SCH-I535 using Bimmer App
Most modern vehicles cut fuel when your foot is off the go pedal. So even though you see the rpm's moving up and down you should understand that most of that is caused by the wheels turning the engine not vice-versa. Bottom line is that it does not negatively impact fuel economy.

Downshifting helps reduce brake wear and as pointed out above puts your trans in the correct gear for moving out again.
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