2013-2020 Lexus GS350 Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2013-2020 Lexus GS350 uses DOT 3 brake fluid. The owner's manual specification section lists the fluid type as SAE J1703 or FMVSS No. 116 DOT 3, and the published maintenance schedule for the GS350 calls for replacing the brake fluid every 30,000 miles. If you live in a humid climate or drive hard in the hills, testing the fluid between those services is cheap insurance.

What Fluid the GS350 Takes and Why It Matters

The fourth-generation GS350 (2013-2020, rear-wheel drive and AWD) runs a conventional glycol-ether hydraulic brake system. The brake specifications page of the GS350 owner's manual lists the fluid as SAE J1703 or FMVSS No. 116 DOT 3. Those are two names for the same class of fluid: SAE J1703 is the industry standard, and FMVSS 116 is the federal safety standard that defines the DOT grades sold in the United States.

FMVSS 116 sets minimum boiling points for each grade. The gap between the "dry" (fresh) and "wet" (moisture-contaminated) numbers is the whole reason a flush interval exists:

These are the federal minimums from FMVSS 116. A given bottle can test higher, but a compliant fluid can never test lower.

Can you use DOT 4 in a GS350?

DOT 4 and DOT 5.1 are glycol-based like DOT 3 and meet or beat every DOT 3 minimum, so they are compatible with a DOT 3 system and are a common upgrade for owners who drive hard. What you must never add is DOT 5 silicone fluid. It is a different chemistry, FMVSS 116 requires it to be dyed purple and labeled "DOT 5 SILICONE BASE", and it does not blend with the glycol fluid already in the car. Glycol fluids (DOT 3, DOT 4 and DOT 5.1) are required to be colorless to amber, so purple fluid in a Lexus reservoir means someone added the wrong product.

How Often to Flush the Brake Fluid on a 2013-2020 GS350

The published maintenance schedule for the GS350 (Base and F Sport) lists "Replace brake fluid" at 30,000 miles, then again at 60,000, 90,000, 120,000 and 150,000 miles. Your own Warranty and Services Guide is the final word for your car, and cars that cover few miles still need attention, because the fluid ages with time whether the car moves or not.

Why fluid wears out without leaking: glycol brake fluid is hygroscopic. It pulls moisture out of the air through hoses and seals and every time the reservoir cap comes off. The industry rates a fluid's "wet" boiling point at 3.7 percent water by volume, which is the point where replacement is due. As water content climbs, the boiling point falls toward that wet number, and the water also corrodes the metal parts inside the calipers, lines and ABS actuator.

Signs your GS350 is overdue

• The pedal gets softer or sinks lower after a long downhill or repeated hard stops, then firms up once the brakes cool. That is classic fade from boiled, wet fluid.
• The fluid in the reservoir is dark brown or cloudy instead of clear to light amber.
• A test strip or electronic moisture tester shows high moisture content.
• You cannot find a record of a flush in the last 30,000 miles.

Checking the Fluid Level Correctly

The reservoir sits on top of the master cylinder, and the level should be between the MAX and MIN lines. Keep two things in mind:

• A slowly dropping level is normal as pads wear. As the pads get thinner, the caliper pistons move out and more fluid sits in the calipers. Topping off a low reservoir on a car with worn pads just means it will overflow when new pads push the pistons back.
• A sudden drop is not normal. Look for wetness at the calipers, flex hoses, hard lines and the back of the master cylinder before driving further.

The manual's brake specifications also list a minimum pad thickness (wear limit) of 0.04 in. If the fluid is low and the pads are near that limit, you have found the reason, and the fix is pads, not fluid.

How the Flush Is Done on This Car

The GS350 has ABS, traction control and stability control built into a hydraulic actuator between the master cylinder and the wheels. A standard pressure bleed or two-person bleed at each caliper replaces the fluid in the lines and calipers, working in the sequence the factory service manual lists. Never let the reservoir run dry while you bleed. If air gets into the ABS actuator, the factory procedure may call for a scan tool to cycle the actuator valves, which is where a DIY job turns into a shop visit.

1. Draw the old fluid out of the reservoir and refill with fresh DOT 3 (or DOT 4) from a sealed bottle.
2. Bleed each wheel in the factory sequence until clean, bubble-free fluid comes out.
3. Tighten the bleeder screws to the value in the factory service manual; they are small and strip easily.
4. Top off to the MAX line, check pedal feel with the engine running, and road test at low speed.

Two cautions: brake fluid removes paint, so cover the fender and rinse any drips with water right away, and do not use fluid from a bottle that was opened long ago, because it has already been absorbing moisture.

What to Replace at the Same Time

A fluid flush is the best time to do pads and rotors, because you will be pushing caliper pistons back and bleeding anyway. On a GS350 with pulsation in the pedal or pads near the wear limit, a 2013-2020 Lexus GS350 front brake kit puts matched pads and rotors on the car in one job. You can also shop individual brake pads and brake rotors, or ceramic brake pads if you want low dust on those large Lexus wheels.

• Rubber brake hoses: if a hose is cracked or swollen, replace it while the system is open. See our brake hoses.
• Hardware and slide pins: new clips and freshly lubricated pins keep new pads from dragging. See brake hardware kits.
• Sticking calipers: internal corrosion from wet fluid is a common cause of a seized piston. If one corner runs hot or the car pulls, look at brake calipers.

How Hard Is This Job?

A brake fluid flush on a GS350 is a moderate DIY job for someone with jack stands, a wrench for the bleeders, clear tubing and either a helper or a pressure bleeder. Buy enough sealed fluid to flush the whole system rather than just the reservoir. The two things that go wrong are letting the reservoir run dry, which can put air into the ABS actuator, and rounding off a seized bleeder screw. If either happens, a shop with a scan tool can finish the job.

Frequently Asked Questions

What brake fluid does a 2013-2020 Lexus GS350 use?

DOT 3 brake fluid meeting SAE J1703 or FMVSS No. 116 DOT 3, per the owner's manual specifications. DOT 4 and DOT 5.1 glycol fluids are compatible upgrades; DOT 5 silicone is not.

How often should I change the brake fluid on my GS350?

The published maintenance schedule lists replacing the brake fluid every 30,000 miles. Low-mileage cars should also be tested periodically, because fluid absorbs moisture over time, not just over miles.

Can I mix DOT 3 and DOT 4 in my Lexus?

Yes. Both are glycol-based and compatible. The blend performs somewhere between the two, so a full flush with one fluid is better than topping off with another.

Why is my GS350 brake fluid low if there is no leak?

Worn pads are the usual reason. As pads wear, the caliper pistons move outward and hold more fluid, so the reservoir level drops. Check the pads before adding fluid.

Does the GS350 need a scan tool to bleed the brakes?

A normal flush at the calipers usually does not, as long as the reservoir never runs dry. If air gets into the ABS actuator, the factory procedure may require a scan tool to cycle it.

What color should Lexus brake fluid be?

Fresh DOT 3 is colorless to light amber. Dark brown fluid is old and contaminated; purple fluid means DOT 5 silicone was added and the system needs a full flush.

Sources

1. Lexus GS350 Owner's Manual, brake specifications - fluid type SAE J1703 or FMVSS No. 116 DOT 3; pad wear limit 0.04 in.
2. 49 CFR 571.116, FMVSS No. 116 Motor Vehicle Brake Fluids - dry and wet boiling point minimums by DOT grade; color and DOT 5 silicone labeling rules
3. Firestone Complete Auto Care, 2016 Lexus GS350 maintenance schedule - replace brake fluid at 30,000-mile intervals
4. ADVICS Aftermarket, Brake Fluid Boiling Points - fluid is hygroscopic; wet boiling point defined at 3.7 percent water; vapor lock risk