How long can I leave it plugged in

I feel like the price of electricity is by far cheaper than the wear on the engine on cold starts in single digits and below.

I've plugged them in for a week at a time in camp, not necessary though. I've seen unplugged Cummins start up when a Ford diesel that's plugged in won't start.

Sheldon

I know of fleets that are plugged in to timers, 30 minutes on and 30 minutes off.

I have personally plugged in power strokes during 20 degree weather and have enough heat after 20 minutes to start them hundreds of times for 25 years with like 6 trucks and have never had a engine failure.

Then I have like 10 internationals that get plugged in, same deal with them, 20 minutes and they will start in 20 degree weather.

Once a year I have to clean the male plug on the trucks with a wire brush to get rid of the corrosion and the female plug on the cord has to be replaced at least once a year because they burn up from the amps that the heaters pull which is close to 1500 watts, like having your toster plugged in 24 hours a day.

I really don't think engine wear is that big of a concern from my 25 years of experience.

We usally leave them plugged in over night, sometimes on Fri night I'll unplug them to save $$ when we are not working the weekend and plug them in 1 hour before starting time on Monday morning and they always start no problem even in the coldest weather.

And I have replaced many cords on the trucks because they get burned up after a few years.

I plugged in my freightliner last weekend for less than a hour and the Cat C-12 motor started with no problem.

You can leave it plugged in as long as you want. Not like the block heater is capable of heating the engine hot enough to do any damage. As for how long you need to plug it in before cranking, well that will boil down to what kind of shape your engine, batteries, etc are in. I know with my 99 cummins 24v if I left it sitting and went to start it anything much below -5f it wasn't happy with me but would start. Now -15f unplugged forget it.

Your grid heater wasn't working correctly. I've seen them start at -40 without being plugged in. The oil is crazy thick and not a good idea but they will start.

Sheldon