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hi, i have a question! All cars i have before at cold days when i start my car it revs for some minutes about 1200rpm and after some minutes the RPM falls to 700! Now my F56 one d in any weather condition start and stay stable at 900RPM !!!!! Is it physical ? thanks
 

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I think technology has moved on somewhat from the crude 'cold start ' choke type higher rev cold start up;these modern engines adjust mixture etc much more efffectively so don't worry it is normal!
 
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One morning, my engine revves up and stays at 800-ish rpm and another morning, it goes up and stays at 1200-ish RPM for a while. I thought it might be something to do with the outside temperature but there seems to be no correlation. I have decided to not worry and just drive fast!
 

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One morning, my engine revves up and stays at 800-ish rpm and another morning, it goes up and stays at 1200-ish RPM for a while. I thought it might be something to do with the outside temperature but there seems to be no correlation. I have decided to not worry and just drive fast!
- It has everything to do with ambient temperature. It's best to let your car fall under 1k RPMs before you take her for a drive.

Tl;Dr
It's normal

Source:
Reddit

It's not actually to warm up the engine for the oil, it has to do with combustion. The requirements are fuel (gasoline), air, and a spark - all under pressure in a precise ratio and timing. This process happens ideally at warmer temperatures (the "operating" temperature) as this is where the fuel vaporizes naturally.
When it's cold, combustion requires much more fuel in the ratio because it does not sufficiently vaporize from liquid gasoline into a gaseous form (liquid gasoline, for the sake of this discussion, does not burn). The problem is, too much fuel through the engine at a low speed bogs down the engine as the unburned liquid fuel will kill the spark and cause it to stall. The RPMs are bumped up to push this fuel out more quickly until a more desirable temperature is attained. Once warm enough, the fuel vaporizes as it should, the computer dials back the fuel mixture (or the carburetor opens the choke) and the RPMs can come down.

and

To everyone saying "your car is trying to warm itself up":
A car is not sentient. It doesn't "try" anything.
High idle is definitely for cold starts, but the higher idle speed isn't simply the result of the car "trying to warm up faster".
Cars used to have carburetors. Now they have fuel injection. Back in the days of carburetors cars had what's called a choke. The choke caused the mixture of air and fuel to have more fuel than it would normally have. Such a mixture is said to be rich. A rich mixture is needed when the engine is cold because the fuel does not evaporate as quickly when it's cold, so more fuel is added to compensate. Modern fuel injected cars don't have a choke, but they also run rich when the engine is cold for the same reasons.
You may not know this, but liquid gasoline doesn't burn. It's the vapors that burn. Therefore: too cold, not enough vapors. No vapors, no fire. No fire, engine doesn't run.
But why does it run at a higher speed? A few reasons... When an engine is cold, there is more resistance to overcome. The oil is thicker, the tolerances are tighter (cold things contract), etc. Another reason is that the engine is running very rich. A rich mixture doesn't make nearly as much power or burn as well as a stoichiometric mixture, and if the engine didn't run at a higher speed it would probably stall. (Stoichiometric means part for part. Not lean. Not rich. Just right.) To put it simply: it's to keep the engine from stalling during cold operation.
And I suppose a beneficial side effect of all of this is that the engine warms up. But that's not the reason why it runs at a higher idle speed.
 
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