I would not leave straight 40 in the winter unless you can always park it indoors. (or unless your winters rarely dip below 20f )If you have a block heater or keep the machine in a heated garage, i wouldn't bother.
I don't live in the cold, how cold does it get? other members may be able to give better advise if they know how cold the machine will get.
Fairbanks, AK. On our road vehicles, we use a block heater and an engine oil pan heater (pad), siliconed on. The pads come in "patches" of various sizes and wattages. Clean the pan, sili it on, and hold w/ pressure till it dries (I use a jack and board). Some folks also put the pad heater on their auto trannies. My JD dealer said that was all they use for year round work. I was also advised not to put a pad heater on a plastic hydraulic fluid tank, as this particular service guy saw one get melted. My opinion is that the thing shorted out and was drawing whatever amps the cord could handle. I don't see how 750 watts could melt anything against hyd fluid that is real cold. I've almost been able to boil water in a paper bag with an oxy-acet torch; never fazed the bag, but I could not get the water to boil. Some kids and I were just dinking around in class one day; however, I digress. Back to the Bobcat. I think you'll be fine with those two, unless you get colder than -50F and plan on working. johnI'm in southern Ontario Canada, it's already starting to get cold here,
last year I kept the bobcat mostly in thr heated shop, but it just took up so much space, I might just leave it in the un-heated barn this winter
I will switch to synthetic 40, that sounds like a good plan