Stopping and starting

Mattyjwr

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We have a 16 yr Merc 312 and I wonder what the optimum time is for turning off the engine - is it better to leave it running while stationary for x mins or turn it off? What is the shortest time it is worth turning the engine off for?
 

Tootles

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If you have a turbo, and/or you have been 'pulling hard' before you stop, it's recommended that you let the engine idle for a few mins before switching off.
 

TheBig1

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many many years! since I was a kid
above advice is correct....let the turbo spin down and cool before switching off. probably about 2 minutes. then switch off if its going to be another 5 minutes. all depends on the health of the starter and charging systems though. no 2 older vehicles are the same

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DBK

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Putting aside turbo issues those on mpg economy competitions will turn off the engine after as little as 30 seconds - but this is with petrol engines and the optimum could be a bit longer for diesels. However, in a queue, think of those stationary near you and turn it off! :)
 
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Mattyjwr

Mattyjwr

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No turbo. The system seems fine. Diesel engine which regularly gets treated but can be a bit smokey so I tend to turn it off but wondered whether I would generate more emissions by turning it on and off regularly or leaving it on.
 
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