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TLDR: Electric driving is severely compromised in cold weather and strongly diminishes the 4XE value proposition.
Longer TLDR: When the temperature is below freezing, the truck will force start the combustion engine even if it has a full battery or is connected to 240V. Short and cold run times on the ICE will cause the car to enter a Fuel and Oil Refresh Mode (FORM). Once in this mode, electric mode is completely unavailable. The process to clear FORM is far from being straightforward.
Context: I purchased this car new in April of 2021. I’ve always been wary of first year model production. I was swayed by the fact that the JL platform was 3 years old and the PHEV technology was mostly transposed from the Pacifica Hybrid. On the reliability front, this has borne true for the most part.
This past summer has been an amazing experience with the Jeep. I was coming fresh off a Tesla Model 3 and this SUV was a perfect solution for electric commuting while also allowing me to pursue activities in the wilderness such as fishing and hunting.
But things have taken a turn for the worse now that the weather is colder. I first noticed that the car would start the internal combustion engine when it was below 0 C (32 F). After reading through the owners manual it described different temperature thresholds for running the ICE. Ok, I can understand the need for additional power to run climate and the drivetrain in cold weather. At first this was not so bad as once the car had sufficiently warmed it would automatically switch to electric mode.
However, this did not last long as the Jeep soon entered the Fuel and Oil Refresh Mode (FORM). Once in this mode, the car would no longer allow any electric usage. The only way to leave FORM requires driving with the oil temperature above 80 C (176 F) for a long time (almost two hours of highway driving in my experience) or resetting the oil life.
This cold weather performance is perplexing to say the least. While I certainly don’t think it was malicious, the first deliveries in significant numbers occurring in March-April did not allow for a true cold weather experience. Moreover, most reviews for the Jeep came out over the summer season and thus could not capture the shortcomings of the vehicle in colder climates.
While I am disappointed of the cold weather performance, hopefully software tweaking could alleviate some of these issues. Disregarding aforementioned issues, the Wrangler 4XE has been a great truck and easily ranks as one of my favourite vehicles I’ve owned so far.
Thanks for reading.
 

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A number of threads on FORM exist already. Sounds like this is a fairly common issue but it does not impact everyone. I live in Western New York - Lots of snow, temps have been single digits. I notice the range decreases from 26 miles to 22 and maybe lower if I have climate turned up and that the vehicle will remote start with ICE if the temp is below 25* or so. Once I start driving, I am able to use all electric without issue unless the temp is <10* then it forces ICE. All in all, it operates as I would expect.
 

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Though I hope software tweaks in the future will fix this and make it less of an impact, this is a fairly well known issue with any electric powered vehicle in winter (at least to me).

Batteries lose efficiency in the cold. As a hybrid, you don’t want electric to switch to gas on a freezing day with a cold engine while you’re driving 70 down the highway. I think the 4xe errs on the side of caution a bit too much with their FORM kicking in and staying on far longer than I’d expect, but otherwise it makes sense. My RAV4 hybrid rarely uses the electric motor in winter, but come summer my efficiency goes way up as the electric motor/battery is much happier.

Unfortunately most if not all companies that have an electric vehicle or PHEV, don’t usually talk about cold weather and their efficiency.
 

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Does anyone know what temperature is needed to evaporate the gas out of the oil? I tried looking but haven't come up with anything definitive.
 

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Does anyone know what temperature is needed to evaporate the gas out of the oil? I tried looking but haven't come up with anything definitive.
Only entered FORM once, only way I was able to get out of it was to bring the oil temp up to 205F. It took a bunch of round town driving and idling to get there. I found highway driving cooled down the temp a bit. Again just my experience and only one time.
 

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Only entered FORM once, only way I was able to get out of it was to bring the oil temp up to 205F. It took a bunch of round town driving and idling to get there. I found highway driving cooled down the temp a bit. Again just my experience and only one time.
I meant in general, not specific to the 4XE. Not well worded looking at it again. In another thread, someone said there are a number of variables so it really depends. The engineers knew that so that's why they determined 205+ I guess. I'll likely invest in a grill blocker at some point to see if that helps it run hotter in winter. Had no form warnings June through end of November. Once it got colder in December is when it started. Probably go away again by end of March, early April although this winter has been pretty mild here.
 

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I meant in general, not specific to the 4XE. Not well worded looking at it again. In another thread, someone said there are a number of variables so it really depends. The engineers knew that so that's why they determined 205+ I guess. I'll likely invest in a grill blocker at some point to see if that helps it run hotter in winter. Had no form warnings June through end of November. Once it got colder in December is when it started. Probably go away again by end of March, early April although this winter has been pretty mild here.
Someone else here in one of the threads has a winter front and seems much happier with the results.
 
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A number of threads on FORM exist already. Sounds like this is a fairly common issue but it does not impact everyone. I live in Western New York - Lots of snow, temps have been single digits. I notice the range decreases from 26 miles to 22 and maybe lower if I have climate turned up and that the vehicle will remote start with ICE if the temp is below 25* or so. Once I start driving, I am able to use all electric without issue unless the temp is <10* then it forces ICE. All in all, it operates as I would expect.
Adding my data point because I have the exact same experience as this, except I live in New England.

Sjbiss is probably an illiterate Bill's fan (they're all illiterate, right?), but he seems to know what he's talking about when it comes to Jeep's and the 4xe.
 

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@Selbeast LOL. Do you think Belichick will let Mac Jones throw the ball 4 times this week? Maybe he is stuck in FORM.
Nah, he ran in FORM during practice all week, so he should be properly lubed for the game. However, it's been cold here this week, so I don't know if he was able to get his oil temp over 200F.
 

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@Selbeast this is the difference in the game. Josh Allen just needed a couple of fuses pushed down and now he back operating as normal. Mac Jones is stuck in FORM and nobody can figure out how to get him it out of it. In fact, he is apparently ruining the planet according to some :)
 

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Welcome to owning a hybrid. Wait till you buy an EV.
My neighbor's Model 3 has no issues driving or charging in the same conditions FORM triggers on my Jeep. Take your disinfo elsewhere. There is a problem. It needs to be addressed. @afroazkhan is absolutely right to be upset and to warn others. Without such complaints, Stellantis will never address the issue. Squeaky wheels, grease, and all.
 

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And yet they still drive in electric. And Tesla doesn't pretend it's not an issue. FORM triggered for me at 0C. This is a problem, and many other PHEVs do not have it so don't pretend it's a thing common to all PHEVs either. It's not.
 

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The wheels on the bus go round and round, round and round, round and round.

I think it is fair to say you two disagree. We got it.
 

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I'm glad I live in AZ, but for how much electricity it takes just for the heater, and how fast batteries drain in cold I can't imagine getting more than 10 miles. At that point it might be cheaper to put gas in. 😁
 

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@ol1bit I get 20-22 electro miles In Buffalo winters. Under 25 or so the vehicle will remote start ICE but allow me to switch to electric when I begin driving. Under 10* it forces ICE. The only time I have seen form is from gas that was 90 days old. I burned off the old fuel and it went away when I refueled.
 

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And yet they still drive in electric. And Tesla doesn't pretend it's not an issue. FORM triggered for me at 0C. This is a problem, and many other PHEVs do not have it so don't pretend it's a thing common to all PHEVs either. It's not.
Well it’s not like Tesla has another option…. Like an ICE.

Still I agree Jeeps is more aggressive than most PHEVs I’ve seen when it comes to this
 
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