746 posts · Joined 2021
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.