2018 Isuzu NPR Fluid Type Specs

Quick Reference

Engine Oil

The 2018 Isuzu NPR is factory-filled with API CK-4 15W-40 heavy-duty engine oil. This is the preferred oil for most climates. In colder temperatures, a 5W-40 synthetic may be used for easier starting. Always use an oil that meets the API CK-4 specification to ensure proper protection for the diesel engine and its emissions components. Never use a gasoline-engine oil (API SP or older) in this diesel engine. Change interval is typically 10,000 miles / 16,000 km, but refer to your owner's manual for the definitive schedule, especially if operating under severe conditions.

Engine Coolant

From the factory, the NPR is filled with Isuzu Genuine Long Life Coolant (LLC), which is a red, OAT-based coolant. It is crucial to never mix this with other coolant types, such as the green or yellow HOAT coolants found in many other vehicles. Mixing coolant chemistries can cause gelling and lead to blockages in the radiator and heater core. If a complete flush is performed, another high-quality, heavy-duty diesel OAT coolant may be used, but for top-offs, it is highly recommended to use the Isuzu-branded fluid. The cooling system should be drained and refilled every 5 years or 150,000 miles, whichever comes first.

Transmission Fluid

The Aisin A465 6-speed automatic transmission in the 2018 NPR requires Idemitsu ATF HP. This is a specific formulation, and using a "universal" ATF is not recommended. While some other fluids may claim to be compatible, for guaranteed performance and longevity, stick with the OEM fluid. The transmission fluid should be changed every 60,000 miles under normal service, or more frequently if the vehicle is subjected to heavy towing or mountainous terrain.

Rear Differential

The rear axle requires a gear oil meeting the SAE 80W-90 GL-5 specification. This is a common and widely available gear oil. There is no limited-slip differential option on this model, so no friction modifier additive is needed. The fluid should be changed every 30,000 miles or 24 months.

Brake Fluid

Like most vehicles on the road, the Isuzu NPR uses standard DOT 3 brake fluid. DOT 4 can also be used, as it has a higher boiling point, but it is not necessary. Never use DOT 5 silicone-based fluid, as it is not compatible with the seals in the brake system. Brake fluid should be flushed and replaced every 2 years, regardless of mileage, as it absorbs moisture from the air over time, which can lead to corrosion and a spongy pedal feel.

Power Steering Fluid

The power steering system in the NPR is filled with Dexron VI automatic transmission fluid. This is a common power steering fluid for many modern vehicles. Do not use a dedicated "power steering fluid" unless it explicitly states that it meets the Dexron VI specification. The fluid should be changed every 60,000 miles or if it appears dark or burnt.

Windshield Washer Fluid

There is no specific technical specification for washer fluid. Use a standard blue "summer" washer fluid in warm climates, and a purple "-20F" or "-30F" winter blend in freezing temperatures to prevent the reservoir and lines from freezing and cracking.

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