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


Use “Ultra Low Sulfur Diesel Fuels (ULSD)” ONLY.

Jeep Wrangler. Cold Weather Precautions

Fuel Operating Range Chart

*Number 1 ULSD Fuel should only be used where extended arctic conditions 0°F (-18°C) exist.


  • 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...

    Engine Idling

    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:

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