2015 Isuzu NQR Fluid Specifications

Quick Reference

Fluid	Type/Spec	Capacity
Engine Oil	SAE 15W-40, 10W-30 (API CK-4)	~10.0 qts (9.5 L)
Engine Coolant	Isuzu Genuine LLC (Red)	~14.1 qts (13.3 L)
Automatic Transmission Fluid	Idemitsu ATF HP	~8.0 qts (7.6 L)
Rear Differential	SAE 80W-90 API GL-5	~7.8 qts (7.4 L)
Power Steering Fluid	GM DEXRON-VI	~2.0 qts (1.9 L)
Brake Fluid	DOT 3	As required
Windshield Washer Fluid		~4.0 qts (3.8 L)
Diesel Exhaust Fluid (DEF)	API Certified (ISO 22241)	~5.0 gal (18.9 L)

Engine Oil

Specification: API Service CK-4 Viscosity: SAE 15W-40 (preferred), SAE 10W-30

For the 5.2L 4HK1-TC turbocharged diesel engine, a high-quality diesel-specific oil is mandatory. The manufacturer specifies an oil meeting API (American Petroleum Institute) service category CK-4. This standard was introduced to provide increased protection against oil oxidation, viscosity loss due to shear, and oil aeration compared to previous categories like CJ-4. It is essential for maintaining the performance and longevity of modern low-emission diesel engines equipped with Diesel Particulate Filters (DPFs).

The preferred viscosity for most operating temperatures is 15W-40. However, in colder climates, 10W-30 may be used to aid in cold starting. Always use a reputable brand that explicitly lists the API CK-4 certification on the bottle.

Change Interval: 10,000 miles (16,000 km). Severe service or high-idle applications may require shorter intervals.

Engine Coolant

Specification: Isuzu Genuine Long Life Coolant (LLC) - Red Type: Phosphate-based Organic Acid Technology (P-OAT)

Isuzu engines require a specific type of long-life coolant to prevent corrosion and ensure proper heat transfer. The factory-fill fluid is a red-colored, phosphate-based OAT (P-OAT) coolant. It is critical not to mix this with other coolant types. Never use conventional green inorganic acid technology (IAT) or even other "universal" extended-life coolants. Mixing chemistries can lead to gelling, which can clog the radiator, heater core, and small coolant passages within the engine, leading to catastrophic overheating.

When topping off or refilling the system, use only Isuzu Genuine LLC or a coolant specifically formulated to meet their P-OAT specification. If a complete flush is performed, the system should be thoroughly cleaned with distilled water before refilling with the correct 50/50 mixture of coolant and distilled water.

Automatic Transmission Fluid

Specification: Idemitsu ATF HP

This vehicle is equipped with an Aisin A465 6-speed automatic transmission. This unit requires a very specific fluid to ensure smooth shifting and clutch performance. The OEM fluid is Idemitsu ATF HP. Using a generic "multi-vehicle" or universal ATF is a significant risk and can lead to shift quality issues, transmission shudder, or premature component failure. Do not use DEXRON, MERCON, or ATF+4 products.

If the original Idemitsu fluid is unavailable, use only an aftermarket fluid that explicitly lists Idemitsu ATF HP as a direct replacement on its data sheet. Fluid and filter changes should be performed according to the maintenance schedule, typically every 30,000 to 60,000 miles, depending on use.

Rear Differential

Specification: SAE 80W-90 API GL-5 Gear Oil

The rear axle differential requires a robust hypoid gear oil meeting the API GL-5 service category. This indicates the oil is formulated with the extreme pressure (EP) additives necessary to protect the ring and pinion gears under high-torque conditions. For most climates, an SAE 80W-90 viscosity is sufficient. In extremely cold environments, an SAE 75W-90 may be substituted for better fluid flow on startup, but it must still meet the GL-5 requirement.

Note: This model does not typically come with a limited-slip differential (LSD). If an aftermarket LSD has been installed, a friction modifier additive must be added to the gear oil to prevent clutch chatter and binding.

Power Steering Fluid

Specification: GM DEXRON-VI

While many commercial trucks use a dedicated power steering fluid, Isuzu specifies the use of DEXRON-VI automatic transmission fluid for the power steering system. This is a fully synthetic, low-viscosity fluid that provides consistent steering feel across a wide temperature range and offers excellent shear stability. Do not use older DEXRON-III or generic power steering fluids, as they do not meet the performance and longevity requirements of this system.

Brake Fluid

Specification: DOT 3

Like most vehicles, the 2015 NQR uses a standard DOT 3 brake fluid for its hydraulic brake system. While DOT 4 fluid has a higher boiling point and is compatible, it is also more hygroscopic (absorbs moisture faster) and is not required. Never use DOT 5 silicone-based fluid, as it is incompatible with the system's seals and will cause severe damage. Brake fluid should be flushed and replaced every 2-3 years, regardless of mileage, to remove accumulated moisture that can cause corrosion and a spongy pedal feel.

Windshield Washer Fluid

Specification: N/A

Use any commercial windshield washer solvent. In winter months, use a fluid with an appropriate freezing point to prevent damage to the reservoir and lines.

Diesel Exhaust Fluid (DEF)

Specification: ISO 22241 / API Certified

DEF is not a fuel additive; it is a consumable fluid injected into the exhaust stream as part of the Selective Catalytic Reduction (SCR) system to reduce NOx emissions. It is a solution of 32.5% urea in 67.5% de-ionized water. Always use DEF that is clearly marked with the API certification or states that it meets the ISO 22241 standard. Using non-compliant fluid can damage the sensitive and expensive SCR system components. DEF has a limited shelf life and can degrade with exposure to sunlight and high temperatures, so always use fresh fluid from a sealed container.

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