2017-2020 Lincoln MKZ Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2017-2020 Lincoln MKZ takes DOT 4 Low Viscosity (LV) brake fluid meeting Ford specification WSS-M6C65-A2, sold by Ford as Motorcraft PM-20. There is no quart-count capacity to hit: Lincoln lists the fill as "between MIN/MAX on brake fluid reservoir." Motorcraft recommends changing this fluid every three years, even though the MKZ's printed maintenance schedule does not list a time-based brake fluid change.

What Brake Fluid the 2017-2020 MKZ Uses

The 2019 MKZ owner's manual (the same generation sold from 2017 through 2020) lists one brake fluid in the capacities and specifications tables for both the 2.0L EcoBoost and the 3.0L V6: Motorcraft DOT 4 Low Viscosity (LV) High Performance Motor Vehicle Brake Fluid, part number PM-20, meeting WSS-M6C65-A2. The manual says you may use an equivalent fluid meeting WSS-M6C65-A2, and warns that any other fluid "may cause degraded brake performance."

The 2016 MKZ owner information lists the same fluid and the same specification, so the fluid choice carries over from the prior model year as well.

Why "Low Viscosity" matters on this car

Federal Motor Vehicle Safety Standard 116 lets an ordinary DOT 4 fluid be as thick as 1,800 mm2/s at minus 40 degrees C. Motorcraft's LV fluid is rated at a maximum of 750 mm2/s at the same temperature. Thinner cold fluid moves faster through the small passages of the ABS and stability-control hydraulic unit, and Motorcraft recommends this formula for ABS systems with stability control, which the MKZ has. The Motorcraft data sheet describes the benefit simply as "a faster response."

A generic DOT 3 or a standard (non-LV) DOT 4 will pour into the reservoir and mix without drama, but it does not meet WSS-M6C65-A2. Buy a bottle that lists the Ford spec or clearly says DOT 4 LV.

What not to use

Motorcraft states PM-20 is compatible with Ford vehicles calling for WSS-M6C65-A2 or WSS-M6C65-A1, and should not be used in vehicles requiring WSS-M6C65-A3 (DOT 5.1 or "Super DOT 4"). Never put DOT 5 silicone fluid in an MKZ either. DOT 5 is silicone based, is dyed purple under FMVSS 116, and is not meant to be mixed with the glycol-based fluid already in the system.

How Often to Flush MKZ Brake Fluid

The MKZ scheduled maintenance tables tell you to inspect the brake pads, rotors, hoses and parking brake at every oil change and to check fluid levels, but they do not list a brake fluid replacement interval. Motorcraft, which makes the fluid Lincoln specifies, is direct about it: the recommended change-out interval is every three years.

The reason is moisture. Brake fluid is hygroscopic: it pulls water from the air through hoses, seals and every time the cap is opened. The federal container label even has to tell buyers to keep the container tightly closed "to prevent absorption of moisture." As water content climbs, the boiling point drops. FMVSS 116 sets a minimum dry boiling point for DOT 4 of 230 degrees C (446 F) but a minimum wet boiling point of only 155 degrees C (311 F). Motorcraft PM-20 is rated at 260 degrees C (500 F) dry and 170 degrees C (338 F) wet. That drop is what turns an old-fluid car into one with a soft, sinking pedal on a long downhill.

A practical plan for an MKZ:

• Every three years regardless of mileage, per Motorcraft.
• Any time you replace a caliper, hose or master cylinder, since the system is opened anyway.
• Sooner if the fluid is dark, a moisture tester shows high water content, or the car sees hard mountain driving.

Checking the Level and Condition

The brake fluid reservoir is marked on the owner's manual under-hood diagrams for both engines. Lincoln's guidance on level is specific: a level between the MAX and MIN lines is within the normal operating range and there is no need to add fluid. Keep the cap fully tightened unless you are actually adding fluid.

Level also drops slowly as brake pads wear, because the caliper pistons move out and hold more fluid. So a level creeping toward MIN on a car with thin pads is often wear, not a leak. If the level is outside the normal range, or the cluster shows "Brake Fluid Level Low," the manual says the brake system should be inspected immediately. Look for wetness at each wheel, at the flexible hoses and at the master cylinder before topping off.

Only add fluid from a sealed container. The manual warns that dirt, water or petroleum products in the system may result in brake system damage or failure. A half-used bottle that has been sitting open in a garage for a year is not fresh fluid anymore.

Doing the Flush on an MKZ

This is a moderate DIY job. The MKZ has four-wheel discs, ABS, stability control and an electric parking brake. The basic approach is a conventional bleed: keep the reservoir from running low so no air reaches the ABS unit, and push fresh fluid through each bleeder until it runs clean. Use the bleed sequence and any scan-tool ABS bleed routine given in the factory service information for your exact model and drivetrain, including the Hybrid.

• Buy a sealed quart of DOT 4 LV (Motorcraft sells PM-20-Q in that size) so you never run short mid-flush.
• A pressure bleeder or vacuum bleeder makes it a one-person job; the two-person pedal method works too.
• Brake fluid removes paint. Cover the fender and rinse any drip with water right away.
• Tighten bleeder screws snugly, and torque the wheels to the value in the owner's manual or factory service information.
• Test pedal feel before driving. A pedal that sinks or feels spongy means air is still in the system.

The manual warns that driving with the electric parking brake applied can damage the brake system. If you are doing rear pad work in the same visit, follow the service procedure for retracting the electric parking brake calipers rather than forcing the pistons back.

Good Times to Pair a Flush With Other Brake Work

Because a flush means opening every bleeder, it pairs naturally with pad and rotor replacement. If you have a shudder in the steering wheel while braking or a continuous squeal or grinding (the manual notes those can mean the linings are worn out), do the parts and the fluid in one weekend. Our 2017-2020 Lincoln MKZ front and rear brake kit covers pads and rotors on both axles. You can also browse replacement brake pads, brake rotors and brake hoses; rubber hoses that are cracked or swollen are worth replacing while the fluid is out. If a caliper is seized or leaking, see our brake calipers.

Frequently Asked Questions

Can I use DOT 3 in my 2017-2020 Lincoln MKZ?

No. Lincoln specifies DOT 4 LV meeting WSS-M6C65-A2. DOT 3 has a lower minimum boiling point under FMVSS 116 and is not the low-viscosity fluid the specification calls for.

How much brake fluid does the MKZ hold?

Lincoln does not publish a volume; the specification is simply "between MIN/MAX on brake fluid reservoir." For a full flush, have a sealed quart of DOT 4 LV on hand.

Is regular DOT 4 the same as DOT 4 LV?

Both meet the DOT 4 boiling-point minimums, but DOT 4 LV is much thinner in the cold. Motorcraft PM-20 is rated at 750 mm2/s at minus 40 C versus a federal DOT 4 ceiling of 1,800 mm2/s. Only an LV fluid meeting WSS-M6C65-A2 matches the MKZ specification.

My MKZ maintenance schedule never mentions a brake fluid change. Do I still need one?

Yes. The schedule only calls for inspections, but Motorcraft recommends changing this fluid every three years because it absorbs moisture and its boiling point drops over time.

Why is my MKZ brake fluid level dropping?

A slow drop tracks with pad wear and is normal. A fast drop or a "Brake Fluid Level Low" message points to a leak or badly worn pads, and Lincoln says to have the brake system inspected immediately.

Sources

1. 2019 Lincoln MKZ Owner's Manual - DOT 4 LV / WSS-M6C65-A2 / PM-20 specification, MIN/MAX fill, brake fluid check warnings, electric parking brake, scheduled maintenance items
2. Motorcraft DOT 4 LV High Performance Brake Fluid product data - part numbers, 750 mm2/s viscosity, 260 C / 170 C boiling points, three-year change-out interval, A1/A2/A3 compatibility
3. 49 CFR 571.116, FMVSS No. 116 Motor Vehicle Brake Fluids - DOT 3/4/5 boiling point and viscosity limits, DOT 5 purple color, moisture labeling
4. Ford Owner Manual, 2016 Lincoln MKZ Capacities and Specifications - same DOT 4 LV PM-20 fluid on the prior model year