Cold Weather Vehicle Prep
Sep 30th, 2008 by C. Alexander Leigh
With our December trip to James Bay, I’ve been looking into the various fluids and greases in the Jeep to figure out what will make the cold (possibly into the -30s) and what won’t. This raises some questions, like, when does ATF fluid freeze?
0W40 Oil: ~ -35C
Mobil 1 Synthetic Grease (front-end, steering): Operating temperature is -40C.
Mobil 1 ATF Synthetic: Pour point is -41C.
Coolant depends on the mix. In a TJ, running 100% water (besides causing corrosion due to caviation) will run the engine temp up to about 149C, which is bad. At least 44% coolant is required to provide corrosion protection. 50/50 provides protection to -37C, and 68/32 coolant/water provides protection to -68C. Beware, because illogically adding more than 68% coolant in the mix results in a warmer freeze point, not a colder one.
If you are running a D30/D35 combo, or regular D44s on your TJ, you’re running 80W-90 in the front and rear. If you have Rubicon D44s, for some reason you are running 75W-140. 80W-90 has a pour point of -42C.
Brake fluid is hygroscopic, so if the fluid is old it should be replaced before embarking on a winter expedition, lest the water in the fluid freeze. Pure DOT4 brake fluid has a pour point around -60C.
You don’t have to worry about petrol at least, if pure, it freezes at about -100C.
I would worry about the battery – make sure you have a good one, like an Optima.