The Ram 3500 uses a long-life, ethylene glycol–based coolant with Organic Acid Technology (OAT). The recommended option is Mopar OEM Antifreeze/Coolant in a 50/50 pre-diluted mix, or any coolant that meets FCA MS-9769 specification and is approved for gasoline or diesel engines. Always verify with the owner's manual or a dealer.
Ram's heavy-duty lineup includes gasoline and diesel options, notably the Cummins 6.7L diesel in many 3500 builds, which places extra demand on the cooling system. The coolant protects against freezing, boiling, and corrosion across a broad operating range and must be compatible with aluminum engine components and the vehicle's additives. Using non-OEM coolant or improper mixing can lead to reduced protection or damage. The following sections outline the specification, sourcing tips, and proper service steps for the Ram 3500 cooling system.
Coolant specification and what to buy
To avoid guesswork, here’s what to look for when purchasing coolant for a Ram 3500:
- OEM approval: Mopar Antifreeze/Coolant, 50/50 pre-diluted, or any coolant labeled as meeting FCA MS-9769 specification and suitable for gasoline or diesel engines.
- Material compatibility: Ethylene glycol–based coolant with Organic Acid Technology (OAT) formulation, designed for aluminum engine components.
- Mix ratio: Use the 50/50 pre-diluted mix unless the specification calls for a different ratio; do not mix incompatible formulas.
- Service interval: Follow the owner’s manual for replacement timing, which for many modern FCA vehicles ranges from several years up to around 150,000 miles, depending on model and engine.
In addition to top-off considerations, ensure you select the correct variant for your engine (gasoline vs diesel), as diesel-specific additives may be required for long-term protection.
Maintenance: how to service the cooling system
Before performing coolant work, prepare with the right safety gear and follow the manufacturer’s procedures. The following steps provide a general guide for Ram 3500 cooling-system maintenance:
- Let the engine cool completely before opening any radiator cap or reservoir to avoid scalding or pressure release.
- Check the coolant reservoir level and the radiator cap label to confirm the required coolant type and mix—use OEM Mopar coolant or an equivalent meeting FCA MS-9769.
- If topping off, ensure you add the same coolant type and maintain the 50/50 mix unless the service manual specifies otherwise.
- If flushing or replacing the coolant, follow the official procedure to drain, flush (if recommended), and refill, making sure the system is free of air pockets and leaks.
- Document the service date and mileage and monitor for any overheating, leaks, or loss of coolant after service.
Adhering to these steps helps ensure the Ram 3500’s cooling system performs reliably under heavy-duty use and varying climates.
Related considerations by engine and model year
Because Ram 3500 configurations vary (gasoline Hemi options, EcoDiesel, and the Cummins diesel in many trucks), always verify the exact specification for your engine and model year in the owner's manual or with a Ram dealer. Some diesel variants may have slightly different additive packages or service intervals, but OEM Mopar coolant meeting FCA MS-9769 is generally the approved baseline for modern Ram heavy-duty pickups.
Summary
The Ram 3500 is designed to run on a long-life, ethylene glycol–based coolant with Organic Acid Technology (OAT). The safest and most reliable choice is OEM Mopar Antifreeze/Coolant in a 50/50 pre-diluted mix, or any coolant that explicitly meets FCA MS-9769 specification and is approved for gasoline or diesel engines. Always consult the owner’s manual or your dealer for the exact requirement for your engine variant and year, and follow proper servicing procedures to maintain optimal cooling performance.