Quote:
Originally Posted by ard
Agreed.
On the singular question of 'saving fuel' turning off the motor may help. But the overall impact on the environment- from how many more batteries need to be made to increased wear to how much emissions a fresh start generates- is a bit harder to calculate.
Seems like a really dumb statement to put in a manual- especially "4 seconds"
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No more batteries are required. A fresh start will generate more emissions if the engine is cold, but not if it is warm. If the engine is warm, the catalytic converter is up to temperature, and the sensors are warm. Theoretically, the starter motor will wear out sooner with more frequent use. There are also other systems which may go through their cycles, as Funf points out. I can't imagine how many components are part of the boot-up cycle of a 35d.
I think the four seconds is illustrative, and not a driving guide. You can save fuel shutting down if the idle is as short as four seconds, but every situation requires the driver to make an intelligent decision on what the best course of action is. The manual doesn't say to shut down if you are idling for four seconds, it points out the fuel saving simply to counteract the commonly held belief that engines should be left idling. Just my $0.02
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2007 X3 3.0si, 6 MT, Premium, White
Retired:
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2003 X5 3.0 Steptronic, Premium, Titanium Silver
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