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Author Topic: Why does my car use more gas/petrol when it is wicked cold?  (Read 4190 times)

Offline Karsten

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Best gas mileage I get in the summer when it is hot. 40 mpg. In the winter when it drops below -10C it is quite bad. 27-30mpg. Why? Same route, same driving behavior. "Wicked cold" is today: -30C.


 

Offline Chemistry4me

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Why does my car use more gas/petrol when it is wicked cold?
« Reply #1 on: 16/01/2009 05:47:15 »
The petrol, or gas, needs more heat in the cold (I think!) making it less efficient.
 

Offline RD

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Why does my car use more gas/petrol when it is wicked cold?
« Reply #2 on: 16/01/2009 06:07:40 »
Air resistance (and consequently fuel consumption) is greater in the cold because cold air is denser: more aerodynamic drag.

« Last Edit: 16/01/2009 06:13:39 by RD »
 

Offline Chemistry4me

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Why does my car use more gas/petrol when it is wicked cold?
« Reply #3 on: 16/01/2009 06:19:55 »
Not to mention trying to drive through the snow! Even more resistance!
 

Offline lightarrow

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Why does my car use more gas/petrol when it is wicked cold?
« Reply #4 on: 16/01/2009 08:01:13 »
Furthermore, if you a have a recent kind of car, the catalytic exaust needs more fuel to work properly.
 

Offline chris

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Why does my car use more gas/petrol when it is wicked cold?
« Reply #5 on: 16/01/2009 08:48:50 »
Most of the increased fuel consumption is accounted for in the cold starting. Petrol engines especially need an enriched fuel mixture when cold because the fuel vapourises less well and so burns less well; the "choke" on the engine overcomes this by enriching the fuel/air mix many-fold (as opposed to manifold!), but consequently the fuel consumption rises accordingly.

The engine is also "stiffer" during a cold start because the oil is much thicker, applying more drag, and the resistance from other bearings around the car is higher when the vehicle is cold because the grease is more viscous and takes longer to warm up.

Chris

The fewer cold starts tjat
 

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Why does my car use more gas/petrol when it is wicked cold?
« Reply #5 on: 16/01/2009 08:48:50 »

 

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