Mine sits outside year 'round. Winters get to -40 F here. I have a block heater, a stick on pad heater on the oil pan sump, and a stick on pad heater on the hydro sump. I have them on a timed outlet to come on in the morning, at least an hour before I know I need the tractor. My OEM Interstate wet cell battery died the first time it hit -30 F. Replaced it with an Optima red top AGM battery, and ZERO battery issues since (2 winters now). I'm also running Amsoil synthetic engine oil. I use the white bottle Power Service additive and run winter red dye fuel. Tractor always starts on the first glow plug cycle.
Other than replacing the stock battery with an AGM, the best thing I did was the oil pan and hydro sump heaters. The hydro heater allows me to start using the tractor almost immediately when it starts. No having to wait until all that hydro fluid warms up and the HST and hydraulic controls start working.
Start it up, let it idle for a minute or two, then bump the idle speed up to 1500 rpms and leave it there until I'm done and shut it down. If you don't bump the idle up, it will actually lose heat and cool off while it's sitting there idling when it's -40 F outside.
