Engine heater best practice - Leave on for 2 days?

[tcal780]

I'm planning a trip to NJ this Friday morning and leaving Sunday morning. Temps will be around freezing for the duration. I have a new sump heater I plan to use for the first time since install.

The airport is about 30 minutes away from where I'm staying. Instructions state 3-5 hours for a cold soaked motor, but I'd prefer not to make two trips or get there early and wait that long. I know keeping an engine heated for an extended period of time is no bueno, but are there any good reasons not to just plug it in when I get there and leave it on for the duration of this 2 day trip?

Thanks,

Tcal

[Fritz1]

perfectly fine to run it for 2 days if airport lets you plug it in, when in doubt bring your own extension cord

[Fly Boomer]

On 12/3/2025 at 11:25 AM, tcal780 said:

Instructions state 3-5 hours for a cold soaked motor

I would be surprised if a sump heater would adequately warm your cylinders in 2-3 hours.  Two days won't hurt.  Once every part of the engine is warm enough to stay above the dewpoint through ambient temperature fluctuations, there won't be any condensation.  Insulating cowling and prop helps keep temperatures normalized throughout your engine.

[AndreiC]

My take, based on recommendation from old timers with a lot of experience here in the Upper Midwest (cold weather) is that usually above freezing heating is not needed, and between 20-32 about an hour is enough with a blanket and cowl plugs. If you can go to the airport with one hour to spare I would do that. Leaving it plugged in for several days seems overkill to me.