Is pre-heating a modern engine worth it?

Question

I have a 2011 Toyota Yaris and live in climate where -5C temperatures are common and -20C are not unheard of. The car has an electric engine pre-heater installed. I don't know exactly what is the type of the electric pre-heater but I don't believe it's of the old type that is installed to the engine core plugs. I have noticed that the pre-heater makes cranking the engine easier when it's very cold. However, I have also noticed that the engine has never failed to start due to cold temperature. So, even though it may take an extra second to start the engine when very cold and the pre-heater has not been used, it does eventually start.

I have seen statements that modern engine pre-heaters are worse than the old core plug block heaters, and thus it's not worth it to use these modern pre-heaters. Is this correct? Does it make sense to use the modern types of engine pre-heaters? I drive only 5500 km per year, but start the engine at least twice per day and am planning to drive the car for at least 15 more years. Is it possible that cold start wear could cause premature engine failure?

There is no electric indoor air heater in the car, so even when pre-heating is used, I have to remove frost manually from the windows. The company I work for has electric outlets in parking spaces but does not allow using indoor air heaters, so if I installed an indoor air heater, I would have to turn it off when parking at the company parking lot and turn it on again when parking in the front of my house.

Answer 1

Modern engine preheaters are usually made of flexible heater mats, similar to those used in seat heaters. These are glued to the bottom of the oil pan. This heats the engine oil. This thins the oil allowing it to pump much more quickly which has two effects.

1) The crankshaft spins faster allowing faster start.

2) The oil reaches the bearings much faster. This is the one that is going to improve engine life since the moving engine parts spend less time with metal to metal contact.

The older style heaters heated the engine coolant. It was much less effective at heating the oil which is the true benefit of preheating an engine.

Note also that it is important to run the engine without load for at least 30 seconds after a cold start. The ensures full lubrication. And it is best to drive very gently for the first few minutes to lessen the possibility of piston ring sticking. A rather unknown cause of engine oil burn, which can happen when the engine is loaded heavily when cold.