Jeep Wrangler: NORMAL OPERATION — DIESEL ENGINE / Cold Weather Precautions
Operation in ambient temperature below 32°F (0°C) may require special
considerations. The following charts suggest these options:
Fuel Operating Range
NOTE:
Use “Ultra Low Sulfur Diesel Fuels (ULSD)” ONLY.

Fuel Operating Range Chart
*Number 1 ULSD Fuel should only be used where extended arctic conditions 0°F
(-18°C) exist.
NOTE:
- Use of Climatized ULSD Fuel or Number 1
ULSD Fuel results in a noticeable decrease in
fuel economy.
- Climatized ULSD Fuel is a blend of Number 2
ULSD Fuel and Number 1 ULSD Fuel which
reduces the temperature at which wax crystals
form in fuel.
- The fuel grade should be clearly marked on
the pump at the fuel station.
- The engine requires the use of “Ultra Low
Sulfur Diesel Fuel”. Use of incorrect fuel
could result in engine and exhaust system
damage.
- If climatized or Number 1 ULSD Fuel is not
available, and you are operating below 20°F
(-6°C), in sustained arctic conditions,
Mopar® Premium Diesel Fuel Treatment (or
equivalent) is recommended to avoid gelling
(see Fuel Operating Range Chart).
Engine Oil Usage
See Engine Fluids and Lubricants for the correct
engine oil viscosity.
Winter Front Cover
A Winter front or cold weather cover can be
used in ambient temperatures below 32°F
(0°C), especially during extended idle
conditions. This cover is equipped with four
flaps for managing total grille opening in varying
ambient temperatures. If a Winter front or cold
weather cover is to be used, the flaps should be
in the full open position to allow air flow to the
cooling module and automatic transmission oil
cooler. When ambient temperatures drop below
0°F (-17°C) the four flaps need to be closed. A
suitable cold weather cover is available from a
Mopar® dealer.
Engine Warm-Up
Avoid full throttle operation when the engine is
cold. When starting a cold engine, bring the
engine up to operating speed slowly to allow the
oil pressure to stabilize as the engine warms up.
If temperatures are below 32°F (0°C), operate
the engine at moderate speeds for five minutes
before full loads are applied.
Observe the following when the diesel engine is
operating:
All message center lights are off.
Malfunction Indicator Light (MIL) is off.
Engine Oil Pressure telltale is not illuminated...
Avoid prolonged idling, long periods of idling
may be harmful to your engine because
combustion chamber temperatures can drop so
low that the fuel may not burn completely...
Other information:
The coolant bottle provides a quick visual
method for determining that the coolant level is
adequate. With the engine OFF and cold, the
level of the engine coolant (antifreeze) in the
bottle should be between the ranges indicated
on the bottle.
The radiator normally remains completely full,
so there is no need to remove the radiator/
coolant pressure cap unless checking for
engine coolant freeze point or replacing
coolant...
WARNING!
Do not attach a tether strap for a rear-facing
car seat to any location in front of the car
seat, including the seat frame or a tether
anchorage. Only attach the tether strap of a
rear-facing car seat to the tether anchorage
that is approved for that seating position,
located behind the top of the vehicle seat...