2019 Isuzu NQR — Complete Fluid Type Specifications

Quick reference

Fluid	Type/Spec	Capacity
Engine oil	Diesel engine oil meeting API CK-4; common viscosities SAE 15W-40 (most climates) or SAE 10W-30 (fuel-economy/colder climates).	Approx 13–16 qt (12.3–15.1 L) incl. filter; verify by VIN/owner’s manual.
Engine coolant	Extended-life OAT/P-HOAT, red/pink. Use Isuzu Genuine Extended Life Coolant or equivalent meeting ASTM D3306/D6210 heavy-duty spec; silicate/borate-free.	Approx 4.0–5.0 gal (15–19 L); verify by VIN/owner’s manual.
Automatic transmission (Aisin 6-speed, A465)	ATF meeting JWS 3324 (Aisin AW-1 / Toyota WS equivalent). Do not substitute Dexron/Mercon types.	Service refill typically 7–10 qt (6.6–9.5 L); dry fill 13–16 qt (12.3–15.1 L). Verify by VIN.
Transfer case (if equipped)	Not applicable — NQR is RWD only.	—
Front differential	Not applicable.	—
Rear differential	API GL-5 hypoid gear oil, typically SAE 80W-90; SAE 75W-90 synthetic acceptable in cold climates. Add friction modifier only if axle is limited-slip.	Approx 3.5–5.5 qt (3.3–5.2 L), axle-dependent. Verify by axle tag/OEM info.
Brake fluid	DOT 3 brake fluid meeting FMVSS 116 (DOT 4 acceptable if specified by OEM; do not use DOT 5 silicone).	Fill to MAX; system capacity varies by brake option.
Power steering	ATF meeting DEXRON-III (H)/MERCON or Isuzu Genuine PSF (ATF-based).	Approx 1–2 qt (0.95–1.9 L); fill to HOT range on dipstick.
Washer fluid	Commercial windshield washer fluid appropriate for climate (premix or concentrate).	Approx 0.8–1.3 gal (3–5 L).
Diesel Exhaust Fluid (DEF)	ISO 22241-compliant 32.5% urea solution (e.g., API-certified DEF).	Typically 4–7 gal (15–26 L), varies by tank option. Verify on vehicle label/OEM info.

Engine oil

• Spec: Use heavy‑duty diesel engine oil meeting API CK‑4 (backward compatible with CJ‑4). ACEA E9/E7 acceptable when paired with CK‑4. There is no separate Isuzu number—Isuzu Genuine Engine Oil meets CK‑4.
• Viscosity: SAE 15W‑40 suits most climates; SAE 10W‑30 CK‑4 for improved fuel economy and cold starts. In extreme cold, consult OEM for 5W‑30/0W‑40 approvals.
• Capacity: Plan for approximately 13–16 quarts including filter, which varies with oil cooler/pan. Always verify by VIN/owner’s manual.
• Interval: Common fleet practice is 10,000 mi (16,000 km) or 400–500 engine hours under normal duty; severe stop‑and‑go, high idle, dust, or PTO use may require 5,000–7,500 mi intervals. Follow the maintenance monitor and used-oil analysis where applicable.
• Pitfalls: Do not use gasoline engine oils (ILSAC passenger‑car oils). Maintain CK‑4 to protect DPF/EGR/Variable‑geometry turbo. Always prime the new oil filter on these medium‑duty diesels when possible.

Engine coolant

• Type: Extended‑life OAT/P‑HOAT, red/pink color, silicate/borate‑free. Use Isuzu Genuine Extended Life Coolant or an equivalent that meets ASTM D3306/D6210 for heavy‑duty diesel applications.
• Capacity: Typically 4.0–5.0 gallons depending on wheelbase and cooler packages; verify in the owner’s manual or OEM service info.
• Interval: ELC is commonly 5 years/150,000 miles initially; subsequent service may be 3 years/100,000 miles depending on product. Top off only with the same chemistry.
• Pitfalls: Never mix conventional green IAT with OAT/P‑HOAT—mixing shortens life and can form gels. Do not add nitrite/molybdate SCA unless the coolant specifically requires it. Always bleed air after service to protect the EGR cooler and heater core.

Automatic transmission fluid (Aisin 6‑speed A465)

• Spec: ATF meeting JWS 3324 (Aisin AW‑1 / Toyota WS equivalent). This low‑viscosity ATF is specific to newer Aisin 6‑speeds—do not substitute Dexron III/VI, Mercon, or “universal” ATF.
• Capacity: Service refill typically 7–10 quarts; a dry overhaul can take 13–16 quarts. Always verify by VIN/trans tag and use the correct dipstick/temperature procedure for level setting.
• Interval: Severe‑duty cycles (urban delivery, high heat, towing) often warrant 30,000–40,000‑mile services; lighter duty can extend to 60,000 miles. Replace the pan gasket/filter where applicable.
• Pitfalls: Using non‑JWS 3324 fluid leads to shift flare and clutch wear. Level must be checked at the specified ATF temp range; over/under‑fill is common cause of issues.

Rear differential

• Spec: API GL‑5 hypoid gear oil. Typical viscosity SAE 80W‑90; SAE 75W‑90 synthetic is acceptable for cold climates or extended service.
• Capacity: Around 3.5–5.5 quarts depending on axle and housing. Confirm by axle tag or OEM spec.
• Interval: 30,000–50,000 miles is common for severe service; highway/light duty can be longer. Inspect magnet and seals at each service.
• Limited‑slip note: If equipped with a limited‑slip or locking differential, follow the axle manufacturer’s guidance. Add friction modifier only if specified; many commercial axles are open and do not require it.

Brake fluid

• Spec: DOT 3 fluid meeting FMVSS 116 (DOT 4 acceptable only if OEM permits). Do not use silicone DOT 5.
• Capacity: Fill to the MAX line; total system volume varies by brake package.
• Interval: Replace every 2–3 years or 30,000 miles. Moisture contamination raises boiling point risk in heavy, stop‑and‑go duty.
• Pitfalls: Keep fluid off paint. Never mix DOT 5 with glycol‑based DOT 3/4.

Power steering

• Spec: ATF meeting DEXRON‑III (H)/MERCON or Isuzu Genuine PSF (ATF‑based). Many N‑Series systems specify ATF rather than generic PSF—check the cap/manual.
• Capacity: Approximately 1–2 quarts. Set level with fluid at operating temperature in the HOT range.
• Interval: Inspect every service; flush if fluid shows discoloration, burnt odor, or aeration.
• Pitfalls: Air entrainment from low fluid or suction leaks causes noise/assist loss. Do not substitute non‑ATF PSF unless explicitly approved.

Washer fluid

• Spec: Any commercial windshield washer fluid suitable for climate (bug remover in summer; de‑icer in winter). Use premix or distilled water with concentrate.
• Capacity: Roughly 0.8–1.3 gallons depending on reservoir option.
• Tips: Keep methanol blends away from painted surfaces when concentrated; avoid household detergents.

Diesel Exhaust Fluid (DEF)

• Spec: ISO 22241‑compliant 32.5% urea solution (AdBlue/DEF). Use sealed containers only.
• Capacity: Typically 4–7 gallons depending on tank option and wheelbase. Verify on the tank label or OEM docs.
• Interval/usage: Consumption is typically 2–3% of diesel fuel usage but varies with duty cycle. The system will warn at low levels and may limit power if empty.
• Pitfalls: Do not add to diesel tank. Store between 23–77°F (‑5–25°C). DEF freezes at 12°F (‑11°C); the truck’s system is designed to thaw it—do not add additives. Keep the fill area clean to avoid SCR injector deposits.

Notes: Specs and capacities can vary with axle, wheelbase, cooler packages, and calibration. When in doubt, verify in the owner’s manual or OEM service information by VIN.

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