You'll want to unplug the block heater before you start the engine for a couple reasons. Mainly so that you don't accidentally drive off with it plugged in, but also so that the extension cord would possibly get wrapped up in moving parts or hot components.
Can you start your car with block heater plugged in?
It won't hurt anything to start it while plugged in.
Does it hurt to leave block heater plugged in all the time?
If you leave it plugged in for longer than 5 hrs in weather over 30 degrees it can scorch the coolant............
Do you unplug the block heater before starting the car?
Either way.... I have done both with no ill effects. Usually, though, I unplug first so I don't forget to. It's just fine to start it with it plugged in... But as you stated, the biggest reason for unplugging before starting is so you don't forget and drive off with it plugged in... Leaving the block heater plugged in shouldn't be a problem.
Is it bad to leave the heater plugged in when starting?
Leaving your heater plugged in when you start the truck won't hurt the engine. It could, however, hurt the block heater. The water around the heater is really warm, and when you start your pickup the water pump could push a bunch of ice cold water by it.
What temperature should a block heater start?
According to car experts, you should get your block heater running immediately when the temperature hits -15°C or -20°C. The argument is based on the fact that your car’s engine can start at -30°C. Getting your block heater running will save your engine from friction, which will be another added advantage to your engine lifespan.
Should you use an engine block heater in cold weather?
By using an engine block heater in a cold climate, your car will start up easier and use less energy. Additionally, because the engine will achieve its optimal running temperature sooner, the driver can put the vehicle under full load sooner without worrying about overstressing the engine.
Below you will find two interesting articles on a similar topic 👇Can I plug my block heater in all night?
At what temperature should you plug your car in?