Question:
I meant when you have your tractor PLUGGED IN so it will start in the cold weather, is the oil level accurate when you check it during your pre trip. I know this is probably a no brainer but sometimes I think too much Thanks.

Answer:
Your truck has been sitting for a few hours with the engine shut off is when you will get the most accurate oil level reading.
All having it plugged in does is to keep the oil and/or coolant warm to ease in flow when it is first started in really cold weather.
Only two things I know of are infinite. The universe and human stupidity, and I am not real sure about the universe.