^A lot of planes use/used straight 30 weight oil or the like.
0W-30/0W-40 oil in a modern synthetic in a car will flows much more easily at sub freezing temps..
They not sell/have in the junkyard/habitat for humanity?:
-Cheap heated/insulated battery blankets where you're at? You literally just need a heating pad around it that will hold up/pop a fuse during a malfunction around the battery and some rock-wool commercial fire-batt around it in an insulating blanket and something to keep the rock wool from absorbing oil/liquid?
-Or the Volvo frost plug replacement block heater?
-Or a 2000W Harbor fright inverter and remote controlled relay to turn on the heater (I mounted mine along the passenger side rear quarter of the wagon for tools/block heat etc).
-Maybe a temporary extra defroster rocker switch for a 240 dashboard and/or remote fob to control all this to minimize having to wait around?
Considerable engine wear & fuel can be saved block heating the car (even after it starts) in extreme cold, even if you're using your Denso 100A alt to inefficiently power the heat source / car battery instead of grid power...
Keep in mind if you've got a little piece of plastic to slide over the intake side/half of the radiator(easy on a 240, just slide it in from the hood slam panel top down really), if it blocks the little hole on the front the intake air box, that hole allows a small amount of air to blow on the wax pellet airbox T-stat while driving, it won't properly regulate the airbox temp to feed the engine ~100% hot air off the exhaust in freezing temps...don't defeat what the guys in white lab coats painstakingly figured out at Volvo. Just a shame the service life of the t-stat is ~ 2-6 years, but it's only like $12 or whatever. Cheaper preventatively than a MAF/Engine/Wasted Fuel &/or fouled Cat/02 sensors.
Also, assume you're running an 87?C or 92?C coolant t-stat? In an N/A car without a water cooled turbo with all that water so close to the exhaust, it's difficult to even get the oil/water up to temp quickly enough to get all the fuel/vapors to come off it in a 240. I ran the water/oil 940 heat exchanger on my N/A car and 92?C T-stat for winter use (probably overkill), bypassed the temp-faker for the temp gauge (of course). Thick "volvo" (or similar phosphate-free decent quality) coolant and a dab of redline water wetter with distilled water. Never changed coolant in a decade or had any corrosion issues with the radiator/hoses. Turbo k-jet cars I'd just run the factory 82?C T-stat year round with water-cooled turbo...warmup was fast and K-jet isn't really affected slightly cooler coolant/intake port walls.
Hopefully the injectors are pretty clean?