Letting a motor warm up in cold weather: Myth or truth?

Question

Current debate between my SO and me: Do you absolutely need to pre-heat a gas car before taking the road in cold weather?

Here in the dead of winter, -10C or lower, its kinda a normal practice to let the gas car run a few minutes before taking the road. Let the motor 'warm up' before going.

I've never quite believed the myth. Sure, you might need the motor to be hot, for the heating to kick in so you can defrost the windshield, but if theres no frost, do you need the pre-heating?

My SO is adamant that in cold weather, if you start the car and immediately put it into drive to go it could cause wear to the motor, or even break things.

On my side, I have a hard time believing it. Especially since our current car is a PHEV and when the battery is gone, the car boots the gas motor, and jumps on it straight to highway speeds. If preheating was needed, they would have a whole preheating bit before jumping to the gas motor.

So who is right? Do you absolutely need to let a gas motor warm up before taking the roads when the weather is cold?

Answer 1

Here in the dead of winter, -10C or lower, its kinda a normal practice to let the gas car run a few minutes before taking the road. Let the motor 'warm up' before going.

I suggest something else. Start driving immediately, but don't load the engine much. Instead, drive gently and don't accelerate quickly. Once the engine is warm, you can use it to its full potential.

However, if you live in an area where you either have to drive up a steel hill, or accelerate to high speed to merge into traffic, then this may not be feasible. In this case, idling for few minutes could be helpful. However, it's a very slow way to let an engine warm up, and idling for two minutes probably causes more wear than doing the same in less than a minute simply by driving gently.

On my side, I have a hard time believing it. Especially since our current car is a PHEV and when the battery is gone, the car boots the gas motor, and jumps on it straight to highway speeds. If preheating was needed, they would have a whole preheating bit before jumping to the gas motor.

This is a major shortcoming of PHEVs, but maybe not in the situation you imagine. Specifically, if you have a PHEV without a decently sized electrical system, once you floor the gas pedal, the electrical system can't supply all of the power and the gasoline engine is going to be loaded hard very suddenly.

However, once the battery charge starts running out, an intelligent control system maybe could anticipate the situation, and gradually let the engine warm with progressively larger power, an in a minute or so the engine has fully taken over.

For example, Toyota hybrids initially prefer battery power when the engine is cold, and then start preferring engine power and charging the battery. The engine is loaded when cold, but not much.