2020 Ford F-350 Super Duty Coolant Capacity & Type Guide

The 2020 Ford F-350 Super Duty holds anywhere from 21.7 quarts up to a massive 41.2 quarts of coolant in total, depending on whether it is equipped with the 6.2L gas V8, the 7.3L gas V8, or the 6.7L Power Stroke turbo diesel engine. As an ASE-certified master technician, I can tell you that getting the coolant chemistry and capacity right on these heavy-duty trucks is absolutely critical, especially if you are towing heavy loads or working the truck in extreme temperatures.

Quick answer

• Total Cooling System Capacity: 21.7 quarts (20.5 L) to 41.2 quarts (39.0 L) depending on engine and heater options.
• OEM Coolant Spec: Motorcraft Yellow Antifreeze/Coolant (Ford specification WSS-M97B57-A1 or WSS-M97B57-A2). This is a Phosphated Organic Acid Technology (P-OAT) coolant.
• Mix Ratio: 50/50 mix of coolant concentrate and distilled water, or a 50/50 pre-mixed solution. In extreme cold climates (below -34°F), a 60/40 coolant-to-water mix may be used.

Capacity by engine option

Because the Super Duty lineup offers multiple heavy-duty powertrains, the coolant capacities vary wildly. Note that the 6.7L Power Stroke diesel actually features two completely separate cooling systems: a primary system for the engine block, and a secondary system for the charge air cooler, transmission cooler, and EGR system.

Note: Capacities are approximate and can vary slightly based on cab size and auxiliary heater prep packages.

Flush interval

Ford transitioned to the Motorcraft Yellow P-OAT coolant to provide exceptional longevity. However, keeping up with maintenance is critical to protect the water pump and aluminum engine components.

• Normal Duty: For standard driving and light-to-moderate towing, the initial factory coolant flush should be performed at 100,000 miles or 5 years. After this initial flush, maintenance should be done every 50,000 miles or 3 years.
• Severe Duty: If your F-350 is a dedicated tow rig, spends extensive time idling (like a work fleet vehicle), or operates in extreme dust and heat, you should check the coolant strength regularly and plan to flush the system every 60,000 miles or 3 years.

How to refill & bleed

Bleeding the cooling system on modern heavy-duty trucks, particularly the 6.7L Power Stroke, can be very difficult without the right tools. Air pockets in a diesel cooling system can lead to localized overheating and catastrophic engine failure.

1. Drain the system: With the engine cold, remove the degas bottle cap(s) and open the radiator petcock(s). Remember the diesel has two separate radiators and degas bottles.
2. Pull a vacuum (Highly Recommended): I strongly advise using a vacuum coolant refill tool (Airlift tool). This hooks up to your shop air and pulls the entire cooling system into a deep vacuum, verifying there are no leaks.
3. Refill: Once a vacuum is established, open the valve to draw your 50/50 Motorcraft Yellow mixture directly into the system. This eliminates 95% of air pockets instantly.
4. Manual Bleed (If vacuum tool unavailable): Fill the degas bottle to the MAX line. Start the engine and turn the heater to the maximum heat/fan setting. Let the engine idle until it reaches operating temperature and the thermostat opens.
5. Hold RPMs: Hold the engine at 2,000 RPM for a few minutes to force remaining air bubbles into the degas bottle. Keep topping off the bottle as the level drops.
6. Cool down and recheck: Shut the truck off, let it cool completely, and check the level one final time.

Common cooling system issues

For the 2020 F-350 generation, keep an eye out for a few specific issues:

• Primary Radiator Leaks (6.7L Diesel): While Ford has improved their radiators over the years, the plastic end tanks on the primary diesel radiator are still prone to developing hairline cracks and weeping coolant under heavy load cycling.
• Water Pump Failures: Weeping from the water pump weep hole is an early indicator of seal failure, particularly on high-idle fleet trucks.
• EGR Cooler Clogging: On the Power Stroke, neglected coolant maintenance allows silicates and degradation byproducts to fall out of suspension, clogging the tiny passages of the EGR cooler and leading to overheating.

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