2018 Ram 3500 Fluid Type Specifications

Quick Reference

Fluid	Type/Spec	Capacity
Engine Oil (6.4L HEMI)	SAE 5W-20, API SN/SP or Mopar MS-6395	7 Quarts (6.6 Liters)
Engine Oil (6.7L Cummins)	SAE 10W-30 or 5W-40 (for cold weather), API CJ-4/CK-4, Cummins CES 20081/20086	12 Quarts (11.4 Liters)
Engine Coolant	Mopar OAT Antifreeze/Coolant, MS-90032 (Purple/Pink)	~18.5 Quarts (6.4L HEMI), ~26 Quarts (6.7L Cummins)
Transmission Fluid (6.4L HEMI)	Mopar ATF+4 Automatic Transmission Fluid	~6.5 Quarts (Service Fill), ~17 Quarts (Dry Fill)
Transmission Fluid (6.7L Cummins)	Mopar AS69RC ATF	~7.4 Quarts (Service Fill), ~13 Quarts (Dry Fill)
Transfer Case (BW 44-46/47/48)	Mopar ATF+4 or Mopar NV247/NV248/NV249 Transfer Case Fluid (MS-9602)	1.6 - 2.0 Quarts (Varies by model)
Front Differential	SAE 75W-90, API GL-5 (with friction modifier for LSD if equipped)	~2.5 - 3.0 Quarts (Varies by axle)
Rear Differential	SAE 75W-140, API GL-5 (with friction modifier for LSD if equipped)	~3.5 - 4.0 Quarts (Varies by axle)
Brake Fluid	DOT 3 or DOT 4	As Required
Power Steering Fluid	Mopar MS-9602 or equivalent (ATF+4 is often specified)	As Required
Washer Fluid	Mopar Windshield Washer Fluid or equivalent	As Required
DEF (Diesel Exhaust Fluid)	API certified, ISO 22241	5.2 US Gallons (19.7 Liters)

Engine Oil

6.4L HEMI V8 (Gasoline)

For the 2018 Ram 3500 equipped with the 6.4L HEMI gasoline engine, the factory-specified engine oil is SAE 5W-20. It should meet or exceed API SN or SP classifications, and ideally carry the Mopar MS-6395 specification. The oil capacity for a filter change is approximately 7 quarts (6.6 liters). It is crucial to use oil that meets these specifications to ensure proper engine lubrication, fuel economy, and to maintain emissions system integrity. Using an incorrect oil type can lead to premature engine wear and potential damage.

• Intervals: Typically every 10,000 miles (16,000 km) or 12 months, whichever comes first, under normal driving conditions. However, the Ram's onboard oil change indicator system should be followed, as it monitors driving conditions to recommend optimal change intervals. For severe duty, intervals will be shorter.
• Common Pitfalls: Never use an oil not meeting the MS-6395 specification, even if it's the correct weight. The additives in the specified oil are critical for HEMI engines, particularly with variable valve timing and cylinder deactivation systems.

6.7L Cummins Turbo Diesel

For the 6.7L Cummins Turbo Diesel engine, the recommended engine oil is SAE 10W-30 for most operating conditions. For consistently cold temperatures (below 0°F / -18°C), SAE 5W-40 is permissible. The oil must be an API certified CJ-4 or, preferably, CK-4 diesel engine oil, and meet Cummins specifications CES 20081 or CES 20086. The oil capacity with a filter change is a substantial 12 quarts (11.4 liters).

• Intervals: The oil change interval for the 6.7L Cummins can vary significantly based on duty cycle, trailer towing, and the use of the Diesel Particulate Filter (DPF) regeneration cycles. Ram's onboard oil life monitor should be followed. Typical intervals range from 7,500 to 15,000 miles (12,000 to 24,000 km) or 6 months. Frequent heavy towing or idling will shorten these intervals.
• Common Pitfalls: Only use low-ash diesel engine oil that meets the CJ-4 or CK-4 specification. Using passenger car oil or older spec diesel oil can damage the emissions system (DPF) and lead to costly repairs.

Engine Coolant

Both gasoline and diesel 2018 Ram 3500 models utilize Mopar OAT (Organic Acid Technology) Antifreeze/Coolant that is purple/pink in color and meets the MS-90032 specification. This is a 10-year / 150,000-mile coolant. Capacities are approximately 18.5 quarts (17.5 liters) for the 6.4L HEMI and around 26 quarts (24.6 liters) for the 6.7L Cummins.

• Intervals: Designed for long-life, typically 10 years or 150,000 miles whichever comes first. However, it's good practice to check coolant levels and condition annually.
• Common Pitfalls: Never mix OAT coolant with other coolant types like HOAT (Hybrid Organic Acid Technology) or traditional green coolants. Mixing can lead to significant chemical reactions, gel formation, corrosion, and severe damage to the cooling system and engine.

Transmission Fluid

6.4L HEMI with 6-Speed Automatic (66RFE)

The gasoline 6.4L HEMI engine in the 2018 Ram 3500 will typically be paired with the 66RFE automatic transmission. This transmission requires Mopar ATF+4 Automatic Transmission Fluid. Service refill capacity is around 6.5 quarts (6.1 liters), while a completely dry fill is closer to 17 quarts (16.1 liters).

• Intervals: Under normal conditions, inspect fluid at 60,000 miles (96,000 km). Replace at 120,000 miles (192,000 km). For severe duty (heavy towing, sustained off-road), inspect and potentially replace more frequently, every 30,000 to 60,000 miles (48,000 to 96,000 km).
• Common Pitfalls: Only use ATF+4. Do not use generic multi-vehicle ATFs unless they explicitly state compliance with ATF+4 and ideally carry the Mopar MS-9602 specification. Using Dexron, Mercon, or other non-ATF+4 fluids will likely cause transmission problems.

6.7L Cummins with Aisin 6-Speed Automatic (AS69RC)

For the 6.7L Cummins diesel, the heavy-duty Aisin AS69RC automatic transmission requires specific Mopar AS69RC ATF. The service refill capacity is about 7.4 quarts (7 liters), with a dry fill capacity of approximately 13 quarts (12.3 liters).

• Intervals: Fluid and filter change intervals for the AS69RC are critical and often recommended more frequently than the 66RFE, especially with heavy loads. Consult your owner's manual or OEM service information for precise intervals, which can range from 30,000 to 60,000 miles (48,000 to 96,000 km) for severe service.
• Common Pitfalls: This transmission is very sensitive to fluid type. Only use the specified Mopar AS69RC ATF. Substitutes can lead to catastrophic transmission failure.

Transfer Case Fluid

Depending on the specific 4WD/AWD system in your 2018 Ram 3500 (e.g., BorgWarner BW 44-46, 44-47, or 44-48), the transfer case generally requires Mopar ATF+4 or a specific Mopar NV247/NV248/NV249 Transfer Case Fluid (MS-9602). Capacity typically ranges from 1.6 to 2.0 quarts (1.5 to 1.9 liters). Always verify the exact transfer case model and fluid in your owner's manual.

• Intervals: Typically every 60,000 miles (96,000 km) for inspection and potentially replacement, or 120,000 miles (192,000 km) for replacement under normal use. Severe duty (off-roading, heavy towing) often necessitates more frequent changes.
• Common Pitfalls: Confirm the correct fluid for your specific transfer case. Some Ram transfer cases are very particular, and using the wrong fluid can lead to premature wear or failure.

Differential Gear Oil

Front Differential

For the front differential, the 2018 Ram 3500 typically specifies SAE 75W-90, API GL-5 gear oil. If your front axle is equipped with a limited-slip differential (LSD), a friction modifier additive must be used or an oil already containing it. Capacity is generally around 2.5 to 3.0 quarts (2.4 to 2.8 liters), but confirm in your owner's manual as it can vary by axle manufacturer and ratio.

Rear Differential

The rear differential usually requires a heavier SAE 75W-140, API GL-5 gear oil, especially given the 3500's heavy-duty nature. Similar to the front, if your rear axle has an LSD, a friction modifier additive is essential. Capacity ranges from 3.5 to 4.0 quarts (3.3 to 3.8 liters).

• Intervals: Inspect at 20,000 miles (32,000 km) and under severe conditions; replace at 40,000 miles (64,000 km). Normal use often extends to 60,000 – 120,000 miles (96,000 - 192,000 km) for inspection, with eventual replacement.
• Common Pitfalls: Always use API GL-5 rated gear oil. Using GL-4 can lead to inadequate protection for hypoid gears. Ensure the correct viscosity is used for front and rear, and definitively use the friction modifier for any LSD-equipped differentials to prevent chatter.

Brake Fluid

The 2018 Ram 3500 requires either DOT 3 or DOT 4 brake fluid. DOT 4 has a higher boiling point and is generally recommended for vehicles that experience heavy braking or towing. Never use DOT 5 (silicone-based) fluid, as it is incompatible with the braking system components.

• Intervals: Brake fluid is hygroscopic (absorbs moisture), which lowers its boiling point over time. It's generally recommended to inspect fluid condition annually and consider a flush and replacement every 2 to 3 years or 30,000 miles (48,000 km), especially in humid climates.
• Common Pitfalls: Never mix DOT 3 and DOT 4 with DOT 5.1, as they have different chemical compositions and can cause system damage. Do not reuse old brake fluid.

Power Steering Fluid

For the hydraulic power steering system, the 2018 Ram 3500 typically specifies Mopar MS-9602 or equivalent. Often, this specification refers back to Mopar ATF+4 automatic transmission fluid.

• Intervals: Check fluid level regularly. Replacement is not typically a routine maintenance item unless contamination or a component replacement occurs. However, some technicians recommend a flush every 60,000 – 100,000 miles (96,000 - 160,000 km) for longevity.
• Common Pitfalls: Using a non-MS-9602 or non-ATF+4 fluid can lead to pump whine or premature component wear.

Washer Fluid

The windshield washer fluid reservoir can be filled with standard Mopar Windshield Washer Fluid or any commercially available, quality windshield washer fluid. For cold climates, ensure it contains antifreeze properties.

• Intervals: Fill as needed.
• Common Pitfalls: Using plain water can freeze in cold weather and damage the system.

Diesel Exhaust Fluid (DEF)

For 2018 Ram 3500 models equipped with the 6.7L Cummins diesel engine and Selective Catalytic Reduction (SCR) system, Diesel Exhaust Fluid (DEF) is required. It must be API certified and meet ISO 22241 specifications. The DEF tank capacity is approximately 5.2 US gallons (19.7 liters).

• Intervals: Consumption varies greatly with driving style and conditions. The vehicle's DEF gauge will alert you when fluid levels are low. Always keep the DEF tank adequately filled.
• Common Pitfalls: Only use high-quality, API-certified DEF to prevent damage to the SCR system. Never put DEF in the diesel fuel tank or diesel fuel in the DEF tank; this will cause severe and costly damage. Do not use expired or contaminated DEF. Store DEF properly as it has a limited shelf life.

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