2019-2020 Jeep Gladiator Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2020 Jeep Gladiator (JT) takes DOT 3 brake fluid that meets SAE J1703; Jeep's owner's manual recommends Mopar DOT 3 for the brake master cylinder. The factory maintenance plan does not list a fixed brake fluid flush mileage. Instead it tells you to inspect the brakes at every oil change and check the fluid whenever the truck is serviced, so the practical interval is set by testing the fluid, not by the odometer.

A quick note on years: Jeep's owner's manual calls the 2020 truck the "All-New Gladiator," so a JT Gladiator bought new in 2019 is a 2020 model year. Check the label on the driver door jamb or your registration if you are not sure. Everything below applies to the gas 3.6L trucks our listed parts fit.

What Brake Fluid the Gladiator Uses

In the Fluids and Lubricants table, the 2020 Gladiator manual lists the brake master cylinder fluid as DOT 3, SAE J1703. It also warns that using the wrong type of brake fluid can severely damage the brake system, and it points out that the correct fluid type is printed on the factory master cylinder reservoir. If your reservoir cap and the manual agree, that is the fluid to buy.

DOT 3 is a federal grade defined by FMVSS No. 116. That standard sets minimum boiling points and requires the glycol-based grades (DOT 3, DOT 4 and non-silicone DOT 5.1) to be colorless to amber. DOT 5 is different: it is silicone-based and must be dyed purple. Silicone DOT 5 does not belong in a Gladiator's glycol system.

DOT 4 beats DOT 3's minimums on paper and is also glycol-based, but the 2020 Gladiator manual names DOT 3. If you want to switch to DOT 4 for towing or trail use, confirm it against the reservoir marking and your dealer first, and do a full flush rather than topping off with a mix.

How Often to Flush the Brake Fluid

The 2020 Gladiator maintenance plan says to inspect brake pads, shoes, rotors, drums, hoses and the parking brake at every oil change interval shown by the oil change indicator. The mileage table adds brake lining inspections and parking brake adjustment on four-wheel disc trucks. It does not include a timed brake fluid replacement. That leaves the fluid's condition up to you and your shop.

Here is why that matters. DOT 3, DOT 4 and DOT 5.1 are hygroscopic, meaning they pull moisture out of the air. ADVICS, a major OE brake supplier, explains that the wet boiling point is measured after the fluid has absorbed 3.7 percent water by volume, and that DOT 3 fluid typically reaches that saturation after about one year of use (about two years for DOT 4). Compare the table above: DOT 3 drops from a 401 F minimum when fresh to a 284 F minimum when wet. Jeep's own manual warns that fluid which has absorbed moisture can boil during hard or prolonged braking and cause sudden brake failure.

A sensible plan for a Gladiator:

• Test the fluid every year with a moisture tester or test strips, ideally at an oil change when the brakes are already being inspected.
• Flush it when it tests high, looks dark or cloudy, or whenever you open the hydraulic system for a caliper or hose job.
• Stay on the short side if you tow, haul or crawl. Long downhill grades with a trailer, and slow off-road descents, put the most heat into the fluid.
• Do it with every pad and rotor job if the fluid is more than a year or two old. You are already bleeding at the calipers.

Symptoms of Old or Low Brake Fluid

• Soft or spongy pedal, especially after repeated stops or on a long downhill. ADVICS lists a spongy pedal and severely discolored fluid as signs a vehicle is overdue.
• Brake warning light. The Gladiator manual says this light monitors fluid level and parking brake application; if it stays on with the parking brake released and the reservoir at the full mark, have the hydraulic system checked right away.
• Dropping fluid level. Jeep notes that the level falls as disc pads wear, so a slightly low reservoir with thin pads is normal. An abnormally low level means a leak until proven otherwise.
• Dark fluid. New glycol fluid is clear to amber. Brown or black fluid has broken down and carries moisture and debris.

Do not fix a low reservoir on worn pads by topping it up to the max line. When new, thicker pads push the caliper pistons back, that fluid has to go somewhere, and Jeep warns that overfilling can spill brake fluid onto hot engine parts where it can catch fire.

Flushing the Fluid: What the Job Involves

A Gladiator brake flush is a manageable job for a careful home mechanic with a helper or a pressure bleeder. The basics:

1. Clean the top of the master cylinder before opening it, as Jeep's manual instructs, so dirt does not fall in.
2. Use only fresh DOT 3 from a sealed or tightly closed bottle. The manual specifically warns that fluid in an open container absorbs moisture and loses boiling point.
3. Remove the old fluid from the reservoir, refill with new, then bleed each wheel in the order shown in the factory service manual until clean fluid comes out.
4. Never let the reservoir run dry while bleeding. Air pulled into the ABS hydraulic unit may need a scan-tool bleed routine to purge.
5. Keep petroleum products (oil, grease, power steering fluid) out of the system. Jeep warns they damage the brake seals.
6. Wipe up spills fast. Brake fluid damages paint and vinyl.

Buy enough fluid for a full flush, not just a top-off; pushing fluid through four calipers plus the reservoir uses more than one small bottle. If the pedal is still soft after a careful bleed, stop and have the system checked before driving.

What to Replace at the Same Time

Because a flush means cracking every bleeder, it pairs naturally with brake work. The Gladiator runs four-wheel disc brakes, so pads and rotors at both ends are the usual candidates. We carry these parts listed for the JT Gladiator:

• EBC Yellowstuff rear brake pads for the Gladiator 3.6L - a high-friction street and tow pad.
• EBC Extra Duty rear brake pads for the Gladiator 3.6L - built for heavier trucks and off-road use.
• Hawk LTS rear brake pads for the 2020+ Gladiator (JT) - a light truck and SUV compound.
• EBC GD Sport slotted front rotors for the Gladiator - slotted faces to help clear pad gases and debris.

Also look at the rubber brake hoses while the wheels are off, especially on lifted trucks where longer suspension travel stretches them. Browse our brake hoses, brake lines and brake hardware kits, or the full brake parts catalog.

Frequently Asked Questions

Can I use DOT 4 in my Jeep Gladiator?

DOT 4 is glycol-based like DOT 3 and exceeds DOT 3's federal boiling point minimums, but the 2020 Gladiator manual names DOT 3, SAE J1703. Check the marking on your reservoir cap, confirm with your dealer, and if you switch, flush the whole system instead of mixing.

Can I use DOT 5 silicone brake fluid in a Gladiator?

No. DOT 5 is silicone-based (federally required to be dyed purple) and is not what the Gladiator's system was filled with. Jeep warns that the wrong brake fluid can severely damage the brake system.

Does Jeep list a brake fluid change interval for the 2020 Gladiator?

Not as a fixed mileage. The maintenance plan calls for brake inspections at every oil change and fluid level checks whenever the truck is serviced. Test the fluid for moisture yearly and replace it when it fails, darkens or the pedal goes soft.

Why is my Gladiator's brake fluid low?

Some drop is normal as the disc pads wear, because the caliper pistons move out and hold more fluid. If the level is abnormally low or the brake warning light comes on, check for leaks at the calipers, hoses, lines and master cylinder before adding fluid.

Should I flush the brake fluid when I replace pads?

If the fluid is more than a year or two old or tests high for moisture, yes. The wheels are already off, and fresh fluid restores the boiling point the new pads and rotors depend on when you tow or descend grades.

Sources

1. 2020 Jeep Gladiator Owner's Manual (FCA US / Mopar) - DOT 3 SAE J1703 fluid, maintenance plan inspections, fluid level checks, brake warning light, moisture and overfill warnings
2. 49 CFR 571.116, FMVSS No. 116 Motor Vehicle Brake Fluids (Cornell LII) - dry and wet boiling point minimums for DOT 3, 4 and 5; DOT 5 silicone and color requirements
3. ADVICS: Brake Fluid Boiling Points and Why They Matter - wet boiling point definition at 3.7 percent water, DOT 3 saturation after about one year, overdue-service warning signs