A cold start is one of the most debated subjects among drivers.
The question is: do you, once the engine is started, drive immediately or leave the car idling for a certain period of time?
Can you drive normally with a cold engine or should you let it gain some temperature first?
Will cold starts damage the engine in the long run?
Hopefully, this article will able to answer these questions, solve the dilemma and provide you with an answer on what’s good for the engine.
WHAT IS A COLD START?
A cold start means starting a vehicle’s engine when it’s cold (obviously). So, the engine hadn’t previously been running and there was no existing working temperature.
If you have the time, click here for an exact and thorough definition provided by Wikipedia.
This is the basic definition. People also regard a cold start as starting the engine in low temperatures or driving when the engine is cold.
WILL LONG IDLING AFTER A COLD START DAMAGE THE ENGINE?
To resolve this question we must dig into car mechanics and automotive history.
First the mechanics part:
In order to start a cold engine, a richer mixture is needed inside the cylinder (more fuel than air).
Besides this, engine oil is needed to lubricate the cylinder and the rest of the vital parts of the engine.
This is where the problem is. The conflict between oil and fuel.
You see, fuel is a very good solvent for oil and during the cold start, it rinses the oil off the cylinder.
What happens in practice: when idling, the air-fuel mixture will stay richer for a longer period of time since the engine temperature climbs slower. This means longer rinsing of oil in the cylinder and this is bad for the engine.
To be honest, this is brief, but if you practice long idling for a longer period of time you may seriously shorten the engine’s lifespan.
This is why starting the car, waiting for a couple of minutes at most, and then driving is best for the engine. The temperature rises faster, the mixture normalizes sooner and the oil pressure is higher.
The next most important thing is knowing how to drive with a cold engine (more on that lower in the article).
I must also mention on this part that long idling is bad for ecology and for travel distance. The fuel you spend idling can cover some serious driving distance. Especially if you multiply it by many times.
WHERE DOES THE DILEMMA COME FROM?
We’ve mentioned the term air-fuel mixture and how important it is for a cold start. In all modern cars, the mixture is regulated by the car’s computer.
Well, It didn’t use to be that way in the past. Now comes the history part.
Before modern electronically overlooked injection systems were invented, cars had carburetors.
In order to start a car, you had to manually regulate the airflow.
It was called pulling the choke and it involved pulling a cable with a button on the end of it.
The cable was connected to a choke plate that blocked off the air going into the carburetor.
Once the car was started and the engine heated up a bit, you pushed the cable back into place, returning the air-fuel mixture to normal.
I must say that this procedure applies to gasoline-driven engines. Most diesel cars were leashed of this, but there were some that had some variant of a choke.
You see, you had to wait for the engine to warm up in order to drive it. If you returned the choke too soon, the engine would cut off.
Also, if you were in a hurry and keen on driving with a cold engine, you would experience somewhat of a rodeo. The car would violently jump, stutter, and probably cut off. If you tried to start it again it could easily flood. You had to be careful.
This is perhaps where the roots of the waiting and idling part comes from. Generations of older drivers had to wait for the car to warm up in order to drive it.
It seems that this information has been relayed over time to younger generations and stuck to this day.
Simply, it turned into a habit over time.
HOW TO DRIVE AFTER A COLD START?
It’s not the same to drive a cold engine and one with a normal, working temperature.
As previously mentioned, the driving style after a cold start plays a big role in prolonging the engine’s lifespan.
The name of the game here: avoid lots of revs when the engine is cold!
Do not go pedal to the metal immediately after you start driving, especially in cold or extremely cold temperatures. This is perhaps one of the worst driving habits.
Although modern engines are built to withstand this kind of torture, you’ll be putting significant and unneeded pressure on the engine and its vital components.
If you try driving like this you’ll sense that the car is a bit sluggish. Also, if you switch the board computer to fuel consumption, you’ll see that it’s at least fifty percent higher.
So what’s the best thing to do?
Once you’ve started the car, wait for a couple of minutes (less in a warmer climate) and start driving at a slower pace.
Gradually increase the tempo as the engine temperature climbs. During that time, don’t drive above 2000 RPMs (for diesel cars) and 3000 RPMs for gasoline (petrol) cars.
As you drive along and the engine temperature increases, the car will become more agile and the fuel consumption will go back to normal and stabilize.
Once the temperature gauge has reached the middle (normal working temperature), you can drive freely and expect 100 percent performance.
Again: drive slow in the beginning and pick up the pace as the temperature goes up.
HOW TO START THE CAR WHEN THE ENGINE IS COLD?
We’ll go from older to newer systems:
Cold start with a mechanical choke
Before starting, pull the choke to the maximum. Pump the gas pedal a couple of times. Crank the engine. Once it’s started, wait for about half a minute and start slowly returning the choke back. It’s a bit tricky, you have to listen to the engine revs and adjust returning the choke to that. Too soon and the engine may cut off, too late and the engine will work on higher revs or even flood.
Cold start with automatic chokes
Here, it depends on the type of automatic choke. For some types, in order to engage it, you must press the gas pedal to the maximum before cranking.
With others, the whole procedure is completely automatic.
These systems were better in terms of comfort as opposed to the mechanical ones, but some car models were very prone to engine flooding because of it.
Cold start on modern cars
As mentioned, computer(s) do all the thinking. All, you have to do is turn the ignition key and start the engine.
The only way you know that the choke is engaged is by higher revs coming from the engine.
A cold start is something to be careful with.
If done improperly it will not immediately damage your engine but it certainly may in the long run.
Avoid long idling as you’re harming your car’s engine, consuming fuel for essentially nothing and, why not say, harming Mother Nature.
Exceptions from this may be extremely low temperatures but that’s another story.
When you start driving with a cold engine, be careful with the gas pedal until the engine gains some temperature. You don’t expect a man to fall out of bed and immediately run a sprint.
Although a lot of us like to sit in a warm car, especially during the winter season, try sometimes staying in your jacket until the interior has warmed. The only exception you should make is when traveling with kids in cold weather. A warm passenger cabin is then a necessity.
So, for the end, when you watch the car idle in the driveway, with a cup of coffee or tea, taking your time to depart, think about how you’re slowly losing money through damaging the engine and unnecessarily consuming all that fuel.
Also, if you’re in a hurry and press a cold engine to its maximum, remember that you seriously shorten its lifespan.
This should be incentive enough to change some habits and make a cold start the right way.
Written by: Sibin Spasojevic
Former car technician, life-long car and DIY enthusiast, author for Despairrepair.com