I know the cummins will start on a cold morning without plugging in the block heater. But I like to plug it in as much as possible. I feel it's better for the motor to have a little warmth. When should I use the block heater, and for how long? Can plugging it in at warmer temps be bad?

 

I don't see what it is gonna hurt being always plugged in except your Electic bill.
I have mine on a timer to come on 2 hours before i leave for work, truck warms up nice and quick.

 

I left mine plugged in whenever i was home last winter , i didn't pay the power bill at my apartment , so as soon as i rolled in the yard after work , it was plugged in , and stayed that way all night.

 

I thought someone told me it was only ment for 20 and below temps. I don't see why it would be a problem for 30 or 40 temps.

 

I thought I read in my manual that it was recommended to use the block heater when the temp. got down to the freezing point. I know it makes a big difference in the time to warm up and the sound of the engine. It also gets heat in the cab quicker..

 

Owners manual for my '01 states recommended below 32*F and required below 0*F, I think, haven't read it in a while. I got tired of busting my knuckles unplugging it and put in a remote starter. If it is forecast for below around 20* I will plug it up though.

 

i plug mine in when i know i'm going to use the truck first thing on cold mornings. My 06 heats up much faster than my 97. dont notice the 06 starting any faster when plugged in, the 97 starts much faster. wish i had a plug in on cold mornings. about 20 is mine and my trucks plug in temp.