Living in eastern PA brings the cold of winter, not too severe but with occasional cold snaps to bring the extra chill. As soon as the weather started moving colder the range on the 4xe definitely decreases. This happens for a few reasons and is expected. Battery efficiency does decrease when the battery is cold but really the biggest cause to loss of electric range of the Wrangler 4xe is from the cabin heater, defroster and the battery heater.
We all want to stay warm inside the Jeep during the cold months, luckily the 4xe features an electric coolant heater which provides warm coolant to the heater when engine heat isn’t available. Electric heat is real nice since it provides near instant heat (windows defrost so quickly) but that high power draw can pull a constant 3-7 kW. In addition to the HVAC system (climate control) the Jeep uses the coolant heater to warm the battery to help it maintain efficiency, this heating draws less power, about 1 kW but it’s still a draw. Watching the hybrid page you can see the power going to the climate system.
In general even internal combustion engines (ICE) are less efficient in the cold but often we just tend to not notice as much. Research shows that ICE vehicles can be 15-20% less efficient in cold weather. A big factor in ICE efficiency is a driveway warm up – 10 minutes idling in the cold is wasted fuel.
In the summer we’ve seen electric range from 21-25 miles, in winter it’s been 17-22.
How to make the most of it?
Pre-conditioning the battery really helps. Using remote start with the Jeep plugged in will turn on the climate system and warm the battery while maintaining charge through the EVSE. Personal experience has shown a 1-2 mile electric gain on average.
Keeping the cabin temp lower and using heated seats and heated steering wheel make a difference. The power drain on the seats and wheel are much less than cabin heat. “Heat the person not the environment”. We have found that 66 degrees on the climate control and heated seat/wheel are very comfortable.
Engine Starting and Fuel Oil Refresh Mode (FORM)
In the cold the ICE will start if the conditions require it. In general if it’s below freezing the ICE will start to supplement cabin heating. Often we’ve had the ICE start during a remote start and immediately shut off as soon as the Jeep is turned on for driving – returning to normal hybrid mode. It’s irritating to hear the ICE running to warm up the Jeep but it’s by design and probably for the best.
Fuel, Oil Refresh Mode (FORM) is kind of a dirty word to 4xe owners. The Jeep enters this mode to maintain the ICE. Without going into a completely technical explanation of this here’s what’s up and why at the link below.
Electric Coolant Heater
Many 4xe owners, including us, have experienced the message “Electric Mode Unavailable, Cabin Heating or Cooling” aka EMU-CHOC. Under normal conditions this is temporary but in most cases it’s an indicator that the electric coolant heater has failed. In this case the only source of heat for the battery and the Jeep’s cabin is the engine.
The jeepfan.com 4xe had a failed coolant heater that did cause the constant EMU-CHOC message(and condition) as well as a check engine light. It took the Jeep dealer a few weeks to get the battery coolant heater in and when it was finally replaced our Wrangler 4xe went back to normal operation.
What’s interesting is that our Wrangler 4xe ran its engine nearly all of the time that the battery coolant heater was not working but the Jeep ran similar to how it runs in FORM (fuel oil refresh mode) – there still is electric pushing the Jeep and a full charge does go down over time and we continued to charge the Jeep when needed. We noticed that the Jeep’s performance is amazing since both electric and engine are working together and to add to it engine fuel economy was better than expected.
This was a good test to measure the MPG of the engine since it ran all of the time making the 4xe act like a non 4xe with a 2.0L engine. For the 5 weeks that the Jeep was working in the EMU-CHOC mode we had a consistent 25-26 mpg. The electric assistance made the 2.0L work a bit less especially during acceleration and hills. A non plugin hybrid version of the Jeep would probably be great by-the-way.
In the end, in the winter the 4xe is still more efficient than a non 4xe Wrangler. We are still getting good fuel mileage and acceptable electric range. So the ICE runs more than it does in the summer..still less fuel being used.