2018 Ford Explorer Transmission Fluid & Service Guide

The 2018 Ford Explorer is a highly capable family SUV, but to keep it shifting smoothly for years to come, staying on top of transmission maintenance is absolutely critical. Whether your Explorer is equipped with the 2.3L EcoBoost, the naturally aspirated 3.5L V6, or the twin-turbo 3.5L EcoBoost, the transmission fluid is the lifeblood of its drivetrain.

As an ASE-certified master technician, I regularly see these vehicles in the shop. Failing to service the transmission can lead to expensive internal damage. Here is your complete guide to the 2018 Ford Explorer transmission fluid type, capacities, and service procedures.

Quick answer

• Transmission make/model: Ford/GM co-developed 6-speed automatic. 6F35 (2.3L EcoBoost and 3.5L V6) or 6F55 (3.5L EcoBoost V6).
• OEM fluid spec: Motorcraft MERCON® LV (Low Viscosity).
• Drain & fill capacity: Approximately 4.0 to 5.5 quarts (6F35) or 4.5 to 6.0 quarts (6F55). Always verify the exact level using the fluid leveling plug.
• Full overhaul capacity: 9.0 quarts (6F35) or 11.6 quarts (6F55).
• Filter OEM part number: The filter is located deep inside the transmission case and cannot be accessed without completely removing and disassembling the transmission. Verify the exact overhaul filter part number with your dealer or service manual if performing a full rebuild.
• Recommended service interval: 30,000 to 60,000 miles (highly recommended), despite Ford's official 150,000-mile claim.

Fluid type explained

The 2018 Ford Explorer requires Motorcraft MERCON® LV transmission fluid. This is a specially formulated, low-viscosity synthetic fluid designed to improve fuel economy, provide excellent thermal stability, and ensure smooth shift quality in Ford's 6F transmission family.

It is crucial that you do not mix this with older Mercon V, Mercon SP, or the newer Mercon ULV. Using the wrong fluid type will lead to incorrect hydraulic pressures, clutch plate degradation, torque converter shudder, and ultimately, premature transmission failure. If you opt for an aftermarket fluid (such as Valvoline MaxLife or Castrol Transmax), ensure the bottle explicitly states it is licensed or approved for MERCON® LV applications. However, staying with the OEM Motorcraft fluid is the safest and most reliable choice.

Service procedure

The 6F35 and 6F55 transmissions do not have a traditional transmission fluid dipstick under the hood, nor do they have a removable bottom pan for filter changes. Because the filter is internal, routine service is limited to fluid changes.

Drain & Fill vs. Full Exchange: A standard drain and fill is the preferred method for most technicians. You simply remove the drain plug at the bottom of the transmission case, let the fluid drain, and reinstall the plug. You then add fluid through the vent/fill port on top of the transmission. Because a significant amount of fluid remains trapped inside the torque converter and valve body, a single drain and fill only replaces about 40% to 50% of the total capacity. To get a higher percentage of new fluid, technicians often perform a "drain and fill, drive, and repeat" process two to three times.

To check the fluid level, the vehicle must be level and running, with the transmission fluid heated to its normal operating temperature (typically between 185°F and 200°F). You then remove the small leveling plug on the side of the transmission case (near the driver's side CV axle). If fluid trickles out, the level is correct.

Flush machines (full exchange) should be used with extreme caution on high-mileage Explorers, as pressurized flushing can dislodge debris and force it into the delicate solenoids of the valve body, leading to shifting issues.

Service interval

Normal Duty: Ford’s official owner's manual states that the transmission fluid does not need to be changed until 150,000 miles under normal driving conditions. As an ASE master tech, I strongly advise against waiting this long. By 150k miles, the fluid is heavily oxidized and saturated with clutch material. I recommend a fluid drain and fill every 60,000 miles for standard highway and city driving to maximize the lifespan of the 6-speed transmission.

Severe Duty / Towing: If you use your 2018 Explorer for towing a boat or trailer, frequent short trips, driving in heavy stop-and-go traffic, or operating in extreme heat/cold, your vehicle falls under the "severe duty" category. The extra heat generated by towing rapidly breaks down MERCON LV fluid. Under these conditions, you should perform a drain and fill every 30,000 miles.

Common transmission problems

The 2018 Explorer's 6F35 and 6F55 transmissions are generally robust, but they do have a few common quirks and issues to watch out for:

• Harsh Shifting and Slipping: Many owners report clunky or harsh shifts, particularly from 2nd to 3rd gear. This is often related to sticking solenoids in the valve body or degraded fluid. Software updates (TSBs) from Ford can sometimes resolve adaptive learning shift issues.
• Torque Converter Shudder: If you feel a vibration or shuddering sensation around 35-45 mph when the transmission shifts into overdrive, the torque converter clutch may be struggling. Fresh fluid often cures this if caught early.
• PTU Failure (AWD Models): While not the transmission itself, the Power Transfer Unit (PTU) bolted to the transmission on All-Wheel-Drive models is notorious for failure. It holds a very small amount of gear oil that overheats easily. It is highly recommended to change the PTU fluid every 30,000 miles to prevent catastrophic failure.
• Axle Seal Leaks: The seals where the CV axles insert into the transmission case are prone to weeping over time, leading to a slow loss of MERCON LV fluid.

Proper maintenance is the key to avoiding these costly repairs. When it's time for your next service, don't leave it to chance.

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