I have purchased a 1988 F350 diesel 1 ton dump and would like to know how often to plug the engine warmer in, during winter?
Is it ok to leave it connected all the time while it sits?
It will be stored outdoors.

When I had an F-350 and F-250 work rigs I plugged them in every night it was gonna drop below 40 degrees. You could tell the difference when I would forget to plug it in overnight. The F-350 was a 6.9 and the F-250 was a Power Stroke.

How long you need to plug it in really depends on the outside temperature, and the overall engine condition.

In general (light to no wind):

>30*F unplugged
20*- 30*= an hour or so
10*- 20* = two hours
0*- 10* = four hours
0* or colder = overnight

This assumes all the glowplugs are in working order, and the batteries are decent.

I've found as long as you plug the sucker in when it gets to 40 degrees farenheit or colder you have no worries.

Leave it plugged in all night, why get up at 2 or 3AM to plug the truck in before work? Leaving it plugged in won't hurt anything.

Could always get a timer, or something, i think it would pay for it's self.