GM's new 3.0L Duramax I6 diesel seems like a real solid engine if you can deal with a half-ton. They supposedly don't need to be plugged in until -14 ish degrees, and run well in the cold and get 27-30 mpg.
I have had a GMC Sierra AT4 with the 3.0 duramax for 2.5 years. Winters in MT are cold.... I mean cold. -30's happens, -20's all the time Dec through Feb, even March. Never had a gel or any issue with cold weather with this truck. And it sits outside (my garage's are packed full of materials and tools and misc. It will delay to start when it gets colder out to let the glow plugs heat up (been winter weather now for 3 weeks, snow won't leave my land at 6100 ft until mid to late June). I think I have had enough timeframe of bitter cold weather with this truck/engine to say that it is doing fine in very cold temps in the winters. Never an issue so far, and I have never read about these 3.0 engines having gel up issues. I've never plugged it in for the block heater even once.
It is a great engine for my needs (contractor). Easily the best pulling/torque engine of any truck I have owned (only owned 1 truck over 1/2 ton size, an early 2000's Ram 3/4 ton with the 360 engine and while that was an old technology truck and engine, this 3.0 duramax out pulls it easily). I have pulled trailers with equipment well over 12K lbs with this truck, it pulls them easily. Pull my job trailer daily during the week, pulls very easy. Gas mileage is about 8 to 10 mpg over a gas comparable truck. It is also quick - not a dog. Plan on keeping the truck longer than my normal 3 to 4 years I usually keep a truck before trading/upgrading. See no reason to do that, especially with the premiums they are asking for new vehicles now. Yes, mine is also worth a lot more, more than I paid for it early April of 2020, but to trade and replace it I would have to still pay premium over priced $ for a newer comparable (if not the same), truck. Makes no sense. 37K miles on this one currently, so have a lot of time to keep it before I need to trade. It will need new tires soon (I never keep the stock tires/wheels), so that will cost me $1600 to replace those. Hoping to get through the winter on this set of tires before replacing. The tread isn't very deep on them at this point, which hurts in snow/ice constant winter driving, but will try to wait until summer to buy a new set of Ridge Grapplers for it.
I had considered selling it - offered near 60K for it straight buy, not on trade, from dealers even this summer. I know a guy who repossesed a 2011 3/4 diesel Silverado he would sell me very cheap - 17 K. That truck would have worked fine for my needs, but of course higher miles, not a great looking truck as it was a SLT trime white work truck model. Would lose all my nice bells and whistles this AT4 sierra has. Was tempting, as I had enough equity in my truck to outright buy the other truck and have some cash left over. But as far as the total package of driving each, this AT4 is a lot nicer ride which doubles as my work truck. Keeping it for several more years at least I think.