Until I saw this post on the HP, I never ever thought about a block heater causing issues from being plugged in too long. But I can't imagine it would be bad? It's not like they keep the engine at operating temperature or anything, so I can't imagine this would cause issues...

 

I always used a timer in my diesel. I'd turn it on about 2hrs before I needed the truck. Obviously this would vary depending on where you live and how cold it was.
I guess the element could go bad if it ran enough hours.

 

Recently I checked the amperage draw on my block heater, 3.5 Eco. Draw was only about 3.5 Amps. Less than 400 watts. Hard to believe there would be any adverse consequences to the engine. Hard to say if there is any chance of burning out the element on the block heater.

 

The time is a great idea.

 

another mostly worthless article.

They never even answer the question posed in the title!!!

Will a block heater plugged in for long periods damage an engine???
The answer of course is NO, providing that it does not malfunction in such a way that the thermostat fails and it overheats. Most likely, even then, it would never be able to produce enough heat to "over-heat" the engine. The engine would do much too good a job of dispersing the heat.

But of course, yes, it will run up your electricity bill. Just like any other electric heater.

Just thought I'd help them out with providing an actual answer to their question.