Basic Engine Warmup Process
Some people think that warming up your car is something you only need to do in the winter, or that it’s only purpose is to warm up the cabin and melt the ice on your windshield. While it does do that, the most important part of the warmup process is allowing the engine to reach the proper temperature before driving, in both spring in winter.
Blue Coolant Light
The simplest way to know your car is ready to drive is if it is equipped with a blue coolant temperature light in the instrument cluster. This feature is mostly equipped on subarus and hondas, but most consumer vehicles without a coolant temperature guage have it.
You might notice this light every time you cold start your vehicle, meaning it has been sitting for several hours and the engine and its fluids have cooled to ambient temperature. It indicates that the engine oil hasn’t warmed up enough to properly lubricate and protect the engine, especially under higher rpms. The light should turn off after a minute or two, at which point the vehicle is safe to drive.
If your car has a regular temperature guage and no blue light, you should watch your tachometer instead to know when you can drive. After a cold start, the engine rpm and sound will elevate for a few seconds. This is because more fuel is sprayed through the injectors to help the engine start, and in colder temperatures, fuel can thicken and the engine compensates by spraying more fuel in. The throttle body then opens to suck in more air and retain the proper air-fuel mixture, thus increasing the engine speed.
The rpms will drop down after a few seconds but still idle higher than a warm engine, to better circulate oil and allow it to heat up. After about a minute the rpms should drop again and the engine will be quieter, indicating that it’s safe to start driving. The rpm range varies depending on the vehicle, but most modern consumer vehicles will idle between 600 and 1,000 rpm when warm.
Dos and Don’ts
It is important to allow your engine to perform its warmup process because over time, driving with a cold engine can damage the internals due to insufficient lubrication from cold oil. This process can take longer in the winter as your engine tries to bring its fluids from below freezing to over 100 degrees.
You should never floor your vehicle or be anywhere near the top end of the tachometer until your coolant guage is right in the middle, indicating the engine is at operating temperature, where it will stay unless it is being overworked or there is a problem with the cooling system.
While it is tempting to let your vehicle idle for ten, twenty, thirty or more minutes in the morning to allow the defroster to melt the ice on the windshield and warm up the cabin, this can do more harm than good in the long run.
One reason for this is fuel consumption. In general, it has been found that an hour of idling burns between ½ and 1 gallon of fuel per hour, so letting your car warm up for 15 minutes every day can get costly just in terms of paying for the additional gas.
Idling doesn’t produce enough heat for your engine to reach its full operating temperature, meaning it won’t be combusting fuel completely which harms its internals and can cause head gasket, spark plugs, or cylinder rings to deteriorate over time.
The engine warmup process usually takes less than two minutes, and in the meantime you can use an ice scraper and brush to remove the ice and snow from your vehicle. Following the process outlined above can save your engine from premature costly wear and tear, as well as save fuel and cut back on harmful environmental emissions.