2016-2018 Lincoln MKX Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2016-2018 Lincoln MKX takes DOT 4 Low Viscosity (LV) brake fluid meeting Ford specification WSS-M6C65-A2, sold by Ford as Motorcraft PM-20. Ford's own product data for that fluid gives a change-out interval of every three years, so plan a full flush on that schedule even though the MKX maintenance tables do not list it as a separate line item.

Below is what the owner's manual actually says for all three model years, why the LV part matters on this SUV, how to tell your fluid is due, and what the flush involves.

What Brake Fluid the 2016-2018 MKX Uses

We checked the Capacities and Specifications chapter in the 2016, 2017 and 2018 MKX owner's manuals. All three list the same fluid in both the 2.7L EcoBoost and the 3.7L V6 tables:

The manual adds a note that Ford recommends DOT 4 LV High Performance Brake Fluid or an equivalent meeting WSS-M6C65-A2, and that using any other fluid may degrade brake performance and fail to meet Ford's performance standards. The Brake Fluid Check section repeats the warning in stronger terms: the wrong fluid reduces brake efficiency and could cause loss of vehicle control.

If you buy a non-Motorcraft bottle, the label needs to say DOT 4 LV (or ISO 4925 Class 6) and ideally reference WSS-M6C65-A2. A plain DOT 4 bottle without the LV designation is not the same product.

Why Low Viscosity DOT 4 Matters on This SUV

DOT 4 LV is still a glycol-based DOT 4 fluid, but it is formulated to stay much thinner when cold. That matters because the MKX relies on its ABS and stability control hydraulic unit to move small amounts of fluid very quickly through small valves. Thinner fluid lets those valves respond faster, especially on a cold morning.

The numbers show the difference. The federal brake fluid standard, FMVSS No. 116, caps ordinary DOT 4 at a kinematic viscosity of 1,800 mm2/s at -40 C. Ford's product sheet for PM-20 lists a maximum of 750 mm2/s at the same temperature, well under half the federal ceiling.

Ford describes PM-20 as meeting FMVSS 116 DOT 4 and ISO 4925 Class 6 and as recommended for ABS systems with stability control, which is exactly what the MKX has.

Can you mix it with other fluids?

Ford's product page lists PM-20 as suitable for vehicles calling for WSS-M6C65-A2 and for the older WSS-M6C65-A1 (DOT 3) specification, and says it is not for systems specified for WSS-M6C65-A3. Never add DOT 5 silicone fluid to an MKX. The safest practice is simple: top off and flush with the exact spec listed in the manual.

How Often to Flush MKX Brake Fluid

This is where owners get conflicting answers. The scheduled maintenance chapter in the MKX manuals lists brake pad, rotor, hose and parking brake inspections at every oil change interval, and caps that interval at one year or 10,000 miles, but it does not list brake fluid replacement as a timed item. Engine air filter, coolant and spark plugs have mileage intervals; brake fluid does not.

Ford's own technical data for the specified fluid fills that gap. The PM-20 product page states the recommended service (change-out) interval is every three years. That is the number we use for the MKX, and it lines up with how glycol fluid ages:

• It absorbs water. Glycol-based fluid pulls moisture from the air over time. That is why federal rules require every brake fluid container to warn buyers to keep it tightly closed to prevent moisture absorption.
• Water lowers the boiling point. PM-20 is rated at 260 C dry but 170 C wet. Boiled fluid makes vapor, and vapor compresses, which feels like a pedal that sinks during a long downhill or repeated hard stops.
• Moisture corrodes the hardware. The ABS valves, caliper pistons and steel lines all sit in that fluid. Old fluid is cheaper to replace than an ABS unit or a set of seized calipers.

If you tow, drive in mountains, or live somewhere humid, flushing a little earlier than three years is reasonable. If the fluid is dark, or a moisture tester shows it is contaminated, do not wait for the calendar.

Signs Your MKX Brake Fluid Needs Attention

• Brake Fluid Level Low message or red brake lamp. The manual says a low brake fluid indication means the brake system should be inspected immediately. A falling level usually means worn pads (the caliper pistons have moved out) or a leak, not that fluid evaporated.
• Level outside MIN and MAX. Ford states that a level between the lines is normal and needs no fluid added, and that a level outside that range could compromise the system and should be checked right away.
• Soft or sinking pedal, especially after hard use. That points to air, boiled fluid or a leak.
• Dark, cloudy fluid in the reservoir. New PM-20 is yellow. Brown fluid has aged.
• Three years since the last flush, or no record of one at all on a used MKX.

Do not simply top off a low reservoir and move on. If the level dropped, check pad thickness and look for wet spots at the calipers, hoses and lines first. If worn pads are the reason, our 2016-2018 Lincoln MKX front and rear brake kit covers both axles in one order.

How the Flush Is Done and What to Replace With It

A flush pushes all old fluid out of the lines, calipers and ABS unit and replaces it with fresh DOT 4 LV. The general approach on the MKX:

1. Clean around the reservoir cap before opening it. Ford warns that dirt, water or petroleum products in the fluid can damage the brake system.
2. Use fluid only from a sealed, fresh container meeting WSS-M6C65-A2. The owner's manual calls for a sealed container specifically.
3. Bleed each wheel in the sequence the factory service information gives, keeping the reservoir from running low so no air enters the ABS unit.
4. Continue until clean yellow fluid comes out at every bleeder, then tighten the bleeders to the value in the factory service manual.
5. Set the final level between MIN and MAX with the cap fully tightened, and confirm a firm pedal before driving.

Glycol brake fluid damages paint and irritates skin and eyes. The manual says to rinse any skin or eye contact with plenty of water and contact a physician. Keep rags under the reservoir and bleeders.

How hard is it?

A pressure bleeder or a two-person pedal bleed is well within reach of a careful DIYer. The catch is air: if the reservoir is ever pumped dry, air can get into the ABS hydraulic unit, and clearing it may require a scan tool that can run the ABS bleed routine. The MKX also uses an electric parking brake, which the manual says recalibrates itself periodically. A fluid flush does not require retracting the rear pistons, but rear pad or caliper work does, so follow the factory service procedure for the electric parking brake before pushing rear pistons back.

Good add-ons while the system is open

• Brake pads and brake rotors if they are near their wear limit, since you are already working at every corner.
• Brake hoses that show cracks, swelling or rust at the fittings. A hose change requires a bleed anyway.
• Brake calipers if a bleeder screw is seized or a piston is sticking. Old, wet fluid is a common reason calipers stop releasing.
• A brake hardware kit so new pads slide freely in the brackets.

Frequently Asked Questions

What brake fluid does a 2017 Lincoln MKX take?

Motorcraft DOT 4 Low Viscosity (LV) High Performance Motor Vehicle Brake Fluid, part PM-20, or an equivalent meeting Ford specification WSS-M6C65-A2. The 2016 and 2018 manuals list the same fluid.

Can I use regular DOT 4 or DOT 3 in my MKX?

Ford says any fluid other than the recommended one may degrade brake performance and not meet its standards. Regular DOT 4 is allowed to be more than twice as thick in the cold as PM-20, which slows ABS and stability control response. Use a fluid labeled DOT 4 LV that meets WSS-M6C65-A2.

How much brake fluid does the MKX hold?

The owner's manual does not give a volume for brake fluid; it says to fill between MIN and MAX on the reservoir. A full flush uses more fluid than the reservoir holds because you push fluid through every line, so buy extra sealed bottles rather than reopening an old one.

Is brake fluid on the MKX maintenance schedule?

The MKX schedule lists brake pad, rotor, hose and parking brake inspections at every oil change, but no timed brake fluid replacement. Ford's product data for the specified fluid recommends changing it every three years, which is the interval we recommend.

Why is my MKX brake fluid low?

Most often the pads have worn and the caliper pistons have moved out, drawing fluid from the reservoir. A leak is the other cause. Inspect the pads and look for wet spots before adding fluid, and have the system checked right away if the warning appears.

Sources

1. 2016 Lincoln MKX Owner's Manual (Ford) - DOT 4 LV, PM-20, WSS-M6C65-A2 for 2.7L and 3.7L; fill between MIN and MAX
2. 2017 Lincoln MKX Owner's Manual (Ford) - same fluid specification for the 2017 model year; Brake Fluid Check warnings
3. 2018 Lincoln MKX Owner's Manual (Ford) - fluid spec, sealed-container and contamination warnings, scheduled maintenance items, electric parking brake
4. Motorcraft DOT 4 LV (PM-20) product data - boiling points, 750 mm2/s viscosity at -40 C, compatibility, three-year change-out interval
5. 49 CFR 571.116, FMVSS No. 116 Motor Vehicle Brake Fluids - DOT 4 minimum boiling points, viscosity limit, moisture labeling requirement