Hello all. We want to reach back out and provide further insight here, as we see that there are still conversations surrounding FORM. Our internal engineers have comprised the following details and we encourage you all to take a look. We have also included the link to the updated Owner’s Manual which now reflects the changes to the section marked “Fuel and Oil Refresh Mode”.
Thanks, Jeep Cares
Further information on the operation of Fuel Oil Refresh Mode (FORM) in the Wrangler 4xe
What is FORM?
Some customers have commented about repeated or extended incidents of Fuel Oil Refresh Mode (FORM) during the winter season. If this is the first time you're hearing about FORM, please refer first to the owner's manual information:
https://msmownerassets.z13.web.core...publications/en-us/Jeep/2021/Wrangler_4xe/P125757_21_JL_H_SU_EN_USC_DIGITAL.pdf
The purpose of this message is to better communicate how the oil dilution portion of FORM works, why some people see it frequently but others don't, and how to get Electric drive mode back. We won't discuss the stale fuel or spark maintenance portions of FORM here, because they are more straightforward and not seasonal in nature.
What is happening in the engine?
Oil dilution FORM exists to reduce the possibility of engine damage caused by contaminants diluted in the engine oil. The contaminant of primary concern is gasoline, since it's continually injected directly into the combustion chamber while running. Although the 2.0-liter turbo 4-cylinder engine in the Wrangler 4xe is manufactured to precise tolerances, piston-ring-to-cylinder-bore sealing varies with engine operating temperature. Sealing is optimized for normal operating temperature. It's normal for some gasoline to make its way past the piston rings when the engine is cold. When the engine becomes warm, the piston rings expand and seal more tightly. Gasoline evaporates out of the hot engine oil, is routed through the Positive Crankcase Ventilation (PCV) system, and is ultimately used to make power.
Is the Wrangler 4xe different from other vehicles?
Oil dilution happens in all internal combustion engines. In conventional vehicles, trips of moderate length are enough to resolve the condition. This is why ICE vehicle owners’ manuals recommend frequent oil changes in vehicles used for short trips. In Plug-in Hybrid vehicles, some use cases lead to many cold engine startups but little or no engine operation at normal temperature. One example is a customer who uses their Plug-in Hybrid Electric Vehicle (PHEV) just like a Battery Electric Vehicle (BEV), except for 0 - 15 minutes' duration ICE operation during most drive cycles. This short engine operation might come during remote start to warm the cabin, or a short high-speed portion of an otherwise all-electric commute. With that type of usage, especially while the outdoor temperature is cold, it's possible for 100% of engine runtime to occur with the engine well below normal operating temperature. Gasoline dilutes into the oil whenever the engine runs, but never evaporates out again. Over time, the contamination level grows.
You won't see features like FORM in BEV's or HEV's, because they're not subject to this use case. But in PHEVs from other manufacturers, you’ll see warnings like "Low Engine Use Mode," "Maintaining Hybrid mode to protect engine," or "Engine Maintenance Mode," which all do the same thing as FORM.
How does the vehicle “know” about dilution? What does it do about it?
It's not practical to directly measure the proportion of gasoline diluted in the oil of a running engine. Before the launch of the Wrangler 4xe, Stellantis engineers built a model which accurately predicts the rate of dilution and evaporation inside the engine. This model runs at all times in the Wrangler's computers, and is based mainly on engine oil temperature, engine load and engine runtime. This is why it's important never to reset your Oil Life Indicator, if you have not changed the oil. To do that would introduce a large error in the modeled vs. actual dilution, and increase the probability of engine damage. Wrangler 4xe owners who encounter dilution FORM have commented that their engine oil smells like gasoline. This indicates that the dilution model is correctly identifying and mitigating a potentially damaging situation.
Dilution FORM in the Wrangler 4xe behaves differently, depending on modeled dilution level.
· Step 0: Normal Operation: Below a bottom threshold, vehicle operation is normal.
· Step 1: Moderate fuel dilution: Between the bottom and middle thresholds, silent start allows electric operation during a drive until the first ICE start. After that, you'll see the FORM message and the ICE will continue running until you shut the car off.
· Step 2: More fuel dilution: Between the middle and top thresholds, EV operation is not allowed. The ICE will start when you power up the vehicle and remain running until you shut down, or the bottom threshold is reached, whichever comes first.
· Step 3: More fuel dilution: Above the top threshold, EV operation is not allowed, and the vehicle will instruct you to perform an oil change.
Depending on outside temperature and how the vehicle is being operated, it could climb or descend this ladder. Based on thorough review of feedback from dealership service departments, directly from customers through Jeep Wave, and from social media postings this winter, Jeep believes some Wrangler 4xe customers' engines are rarely warming fully to operating temperature. For this reason, oil dilution is staying between the bottom and middle thresholds (“Step 1”) for extended periods of time in some vehicles operating in cold climates. The user's experience is therefore similar to frequently leaving and re-entering dilution FORM. Some customers may also be experiencing extended periods in “Step 2.” Jeep Engineering and Jeep Wave are not aware of any cases where FORM is acting differently than designed, or where an unrelated hardware issue is exacerbating FORM duration or frequency.
How can I get Electric mode back?
The use case which leads to this level of dilution can vary, but the path to resolution is always the same:
· Start the engine and allow engine oil to reach normal operating temperature. 169°F (76°C) is the minimum, but normal operating temperature is above 194°F (90°C). Elevated speed and load will warm the engine oil most quickly.
· Continue running the engine until FORM is no longer shown in the Message Center of the instrument cluster. Depending on the dilution level, oil temperature and outside temp, this can take from 20 minutes to 2.5 hours.
· In case the above steps are not possible, change the engine oil and reset the oil life indicator.
· Never reset the oil life indicator without changing the engine oil.
It's possible that some use cases lead to a lot of dilution and not enough evaporation to compensate. In this case FORM will return as long as the weather remains cold. We have high confidence that these frustrations will be resolved when the weather becomes warmer.
