Optimal oil for lethally cold weather, Jeep 4.0L, parked outside

You don't need to do anything special other than use 5w-30 or 0W-40 engine oil and make sure you have a good battery. If you will be parked out of range of an extension cord, a solar-powered battery tender might be a good solution.
 
More important than your oil choice is getting a good battery. Highest CCA that will fit although -15 to -20F isn't that cold in reality. We park outside and have 2-3 weeks in a row some years more where the day time high doesn't cross 0F and lows bottom out at -30F to -40F, we run a 5w-30 in all our vehicles and the only thing keeping them from starting is a weak battery. Block heater will help a ton but probably not needed at those temps.
 
As I recall the electronics of the '88 4.0l I6 (sister had one-a 2 door Pioneer in Fire Engine Red with factory white wheels-THE ultimate girl car) involved counters zeroing both the ignition and fuel injection circuits.
This meant that the engine had to crank a bit EVERY TIME you started the engine-to get through 2 "zeros".
This priming will help that engine last.
 
Isn't South Bend somewhat surrounded (on the northern sides) by the Great Lakes? Do Lakes Michigan & Huron still freeze over in winter (like in the '70s)? I would think a good set of snows ot A/Ts would be more important than oil, any old 5W30 or 0W30 synthetic & a good battery & starter would do it.
 
So several of you mentioned engine block heaters. I don't know anything about those. What powers them? Someone mentioned never seeing outlets at every parking spot until they went to Canada or Minnesota or something. There won't be room in the garage for the Jeep, so it's the odd man out. Will I have to run an extension to power a block heater? I assume they're electric, and not some chemical reaction warming pack, since those probably wouldn't last long enough.

This reminds me of a battery issue I was thinking about. It's not going to be my daily driver, so I want to use a battery tender or similar. But they all seem to need to be plugged into wall power. How do people use them for vehicles parked outside? I've searched for "portable battery tender" or "standalone battery tender", but I haven't had any luck. My visual here is a battery-powered battery tender, which seems super doable. Lots of compact battery designs and types could work for just trickle charging a car battery for a few weeks at a time. People on other boards got hung up on the assumption that a battery tender has to be plugged into wall power, or else where is the juice coming from? The answer is that it can simply come from a battery. I might try to just make my own. Have you seen any products? (I wonder if it's even possible for a battery to tend itself, if you could basically harvest or divert some of the drain right back to the terminals – it would still be a net loss over time, but it could be a big reduction in the drain rate depending on how the math hashes out.)
 
Isn't South Bend somewhat surrounded (on the northern sides) by the Great Lakes? Do Lakes Michigan & Huron still freeze over in winter (like in the '70s)? I would think a good set of snows ot A/Ts would be more important than oil, any old 5W30 or 0W30 synthetic & a good battery & starter would do it.
Normally no. The only lake that reliably freezes over is Lake Superior. Rare is it when it does not.
 
For the record lows in South Bend a synthetic 5w-30 will do fine. I used Amsoil 0w-30 in my Jeep 4.0 when I lived in Montana, with numerous cold starts going as low as -35F. It made a difference once below about 15F.

That said agree that M1 0w-40 is a good choice; you may also want to consider a 5w-40.
Mobil 1 0w30 in our Hummer H3 at -38 in Great Falls MT.
 
If you are considering Amsoil, HDD 5W-30 would be a great option for this old-school style engine.
 
Isn't South Bend somewhat surrounded (on the northern sides) by the Great Lakes? Do Lakes Michigan & Huron still freeze over in winter (like in the '70s)? I would think a good set of snows ot A/Ts would be more important than oil, any old 5W30 or 0W30 synthetic & a good battery & starter would do it.
I don't remember which lake, but South Bend is supposed to suffer from a "Lake Effect" climate. It's unusually cold for Indiana.
 
I don't remember which lake, but South Bend is supposed to suffer from a "Lake Effect" climate. It's unusually cold for Indiana.
The Lake Effect climate is due to the cold north winds off of Lake Michigan.

0A05AFCE-303E-4B0B-9DEC-079AE9EF7A1F.png
 
The typical noise complaints were from AMC derived engines. The only one on your list that falls into that would be the 2.5L and then only if it was AMC and not the GM Iron Duke.
It was the AMC. It was in my 93 Wrangler. But I've heard people say it about other makes of engines, not just Jeeps. I've never heard it in any engine.
 
The Lake Effect climate is due to the cold north winds off of Lake Michigan.

View attachment 61097

But the "lake effect" climate is a moderating one, the winters are warmer while the summers are cooler. For example Milwaukee generally has warmer winters than inland Wisconsin.

More evidence that this entire thread is based on a flawed premise that South Bend has "lethally" cold weather.
 
I believe “The Lake Effect” is more of a snow issue. Here is a screen capture showing the areas around the Great Lakes, but even so, South Bend is just outside the region that gets snow the most.

B3A5431D-287D-4289-A50B-2382EC509237.jpg
 
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