2018 Freightliner M2 106 Fluid Type Specifications & Capacities

As an ASE-certified master technician, I know that medium-duty commercial trucks like the 2018 Freightliner M2 106 are the lifeblood of countless fleets. These workhorses are built for extreme durability, but that reliability hinges entirely on proper maintenance and using the exact fluids specified by the manufacturer. Using the wrong oil, coolant, or transmission fluid won't just sideline your truck—it can lead to catastrophic component failure that costs tens of thousands of dollars.

Below is your complete, ASE-backed fluid specification guide for the 2018 Freightliner M2 106. Note that because this chassis can be customized with different engines (commonly the Cummins B6.7, Cummins L9, or Detroit DD5/DD8), transmissions (Allison automatics, Eaton manuals), and axles, capacities will vary. Always verify your specific setup using your VIN and OEM service info.

Quick reference

Fluid	Type/Spec	Capacity
Engine Oil (Cummins B6.7)	15W-40 or 5W-40 Full Synthetic; API CK-4, Cummins CES 20086	15.0 - 17.5 quarts (with filter)
Engine Oil (Detroit DD5)	15W-40 or 5W-40 Full Synthetic; API CK-4, Detroit DFS 93K222	18.0 - 20.0 quarts (with filter)
Engine Coolant	Nitrite-Free OAT (Red/Magenta); Cummins CES 14603 or DDC 93K217	25.0 - 32.0 quarts (varies by heater)
Transmission (Allison Auto)	Allison TES 295 (TranSynd) or TES 668	15.0 - 19.0 quarts (varies by pan)
Transmission (Eaton Manual)	Eaton PS-386 Synthetic Transmission Fluid	12.0 - 24.0 pints (varies by model)
Differential (Rear Axle)	75W-90 or 80W-140 Synthetic; API GL-5, SAE J2360	14.0 - 24.0 pints (varies by axle)
Brake Fluid (If Hydraulic)	DOT 4 Brake Fluid (Note: Most M2s use Air Brakes)	Verify in owner's manual
Power Steering	Dexron III / TES 389 ATF or 15W-40 (check cap)	~3.0 - 4.0 quarts
Diesel Exhaust Fluid (DEF)	API Certified DEF; ISO 22241	5, 10, or 13 gallons (varies by tank)
Windshield Washer	Standard -20°F Washer Fluid	~1.0 gallon

---

Engine Oil

The engine oil requirements for the 2018 Freightliner M2 106 depend heavily on which engine was spec'd at the time of purchase.

• Cummins B6.7 or L9: Requires heavy-duty engine oil meeting the API CK-4 standard and Cummins CES 20086 specification.
• Detroit DD5 or DD8: Requires oil meeting the API CK-4 and Detroit DFS 93K222 specifications.

For optimal wear protection and fuel economy, a 5W-40 full synthetic is highly recommended, especially in colder climates, though a conventional or synthetic-blend 15W-40 is standard for normal to hot climates. Common Pitfalls: Never use older API CJ-4 oils unless you are in a pinch, as CK-4 provides vastly superior aeration resistance and oxidation control vital for modern emissions systems. Oil change intervals typically range from 15,000 to 30,000 miles depending on idle time and duty cycle—never ignore your engine hours when calculating service intervals.

Engine Coolant

Modern medium-duty diesel engines rely heavily on advanced coolant chemistries to prevent cylinder liner cavitation and protect the EGR cooler. Your M2 106 requires a Nitrite-Free Organic Acid Technology (OAT) coolant.

• For Cummins engines, look for Cummins CES 14603 (like Fleetguard ES Compleat OAT).
• For Detroit engines, look for DDC 93K217.

Common Pitfalls: Do NOT mix OAT coolant (typically red or magenta) with older HOAT (Hybrid OAT) or conventional green coolants. Mixing coolant chemistries can cause the additives to drop out of suspension, forming a sludge that will clog the heater core and EGR cooler, leading to severe overheating and engine failure.

Transmission Fluid

Most 2018 M2 106 trucks are equipped with an Allison 2000 or 3000 series automatic transmission. These transmissions require a fully synthetic fluid meeting the Allison TES 295 specification (such as Castrol TranSynd) or the newer, backwards-compatible TES 668 spec. If your truck has an Eaton Fuller manual or automated manual transmission (AMT), you must use a synthetic transmission fluid meeting the Eaton PS-386 specification. Common Pitfalls: Never use universal "Multi-Vehicle" ATF in an Allison commercial transmission. Universal fluids lack the shear stability required for heavy towing and will void your Allison warranty.

Differential / Drive Axle Fluid

The M2 106 is usually outfitted with Meritor or Dana Spicer rear axles. Regardless of the brand, they require a high-quality full synthetic gear lubricant meeting API GL-5 and SAE J2360 standards. A 75W-90 full synthetic is standard for most highway and regional duty cycles, while 80W-140 may be recommended for severe duty or off-road applications. Common Pitfalls: Avoid using conventional 80W-90 gear oil. Synthetic fluids are required to meet the extended 500,000-mile drain intervals specified by Meritor and Dana. Conventional oil will break down under heavy load and heat, severely shortening bearing and gear life.

Brake Fluid (and Air Brakes)

The vast majority of 2018 Freightliner M2 106 trucks are equipped with full air brakes. Air brakes do not use hydraulic brake fluid; instead, they rely on an air compressor, tanks, and an air dryer. It is critical to service your air dryer cartridge annually to prevent moisture buildup in the lines, which can freeze or cause corrosion. If your specific M2 106 was ordered with optional hydraulic brakes, it uses DOT 4 hydraulic brake fluid. Flush the DOT 4 fluid every 2 years to prevent moisture absorption, which lowers the boiling point and rusts internal ABS components.

Power Steering Fluid

Freightliner typically specifies a standard Dexron III ATF or a fluid meeting Allison TES 389 for the TRW power steering gears in the M2 chassis. However, some heavy-duty setups may utilize 15W-40 engine oil in the steering system. Common Pitfalls: Always check the cap on the power steering reservoir or consult your owner’s manual before topping off. Mixing ATF with 15W-40 will alter the viscosity and could lead to seal damage or poor steering assist in extreme temperatures.

Diesel Exhaust Fluid (DEF)

To keep the SCR (Selective Catalytic Reduction) system functioning and avoid engine derate, you must use Diesel Exhaust Fluid that is API Certified and meets the ISO 22241 standard. Common Pitfalls: DEF has a limited shelf life, especially in high heat. Never pour old, degraded, or contaminated DEF into your tank. Even a small amount of dirt, diesel fuel, or tap water can permanently destroy the SCR dosing valve and catalyst—a repair that can easily top $5,000. Keep your DEF tank full in cold weather to reduce air volume and minimize freezing, although the system has built-in heaters to handle frozen DEF upon startup.

Windshield Washer Fluid

Use a high-quality, standard washer fluid rated for your local climate (typically -20°F in winter). In commercial trucks, keeping the windshield clear is a massive safety requirement, so ensure the reservoir (which holds roughly 1 gallon) is topped off during every pre-trip inspection.

---

Proper fluid maintenance is non-negotiable for commercial trucks. Keeping up with OEM-specified intervals using the right chemicals keeps your freight moving and your repair bills low. Find a trusted shop on Repairius.