2013-2018 Cadillac ATS Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

Every 2013-2018 Cadillac ATS leaves the factory with GM-approved DOT 3 brake fluid, and that is what goes back in at service time. GM's published maintenance schedule for the ATS says to change the brake fluid on a mileage interval or every 3 years, whichever comes first, so most owners reach the time limit before the mileage one. ATS-V owners who take the car to a track are the exception: GM says to use a higher-boiling fluid for track days and flush it back out afterward.

What brake fluid the Cadillac ATS uses

The ATS owner's manual is plain about it: the brake/clutch master cylinder reservoir is filled with GM-approved DOT 3 brake fluid, and the correct fluid is also marked on the reservoir cap. DOT 3 is a glycol-ether fluid built to the federal standard FMVSS 116, which sets minimum boiling points for every fluid sold as DOT 3, DOT 4 or DOT 5.

Note the words "brake/clutch." On manual-transmission ATS models the clutch hydraulics draw from the same reservoir as the brakes, so the fluid you use and how clean you keep it affects clutch feel as well as braking.

The "wet" number is the minimum boiling point after the fluid has absorbed water, and that is the number that matters on a car that has gone years without a flush. Never put DOT 5 silicone fluid in an ATS. GM's high-performance brake fluid bulletin that covers the ATS-V states directly that DOT 5 is not compatible with these brake systems.

Cadillac ATS brake fluid flush interval

GM's maintenance schedules for the ATS sedan (the 2015 and 2016 schedules are both published on GM's owner site) list "Change brake fluid (or every 3 years, whichever occurs first)" alongside the scheduled mileage services. The mileage point is marked on the schedule grid for your model year, so check the maintenance schedule in your owner's manual or on GM's owner center for your exact car. In practice the 3-year clock is what triggers the service for most ATS owners, because an average commuter will not reach the mileage point that quickly.

Why a time limit at all? DOT 3 fluid is hygroscopic: it pulls moisture from the air through the reservoir vent, hose walls and seals whether the car is driven or not. ADVICS, a major OE brake supplier, explains that once fluid has absorbed about 3.7 percent water by volume it is considered saturated, and that DOT 3 formulas typically get there in about a year of use, with DOT 4 around two. That water drags the boiling point down toward the wet number in the table above and starts internal corrosion in the calipers, lines and ABS unit.

• Normal driving: follow GM's schedule - every 3 years at the latest.
• Towing, mountain driving, hard street use: flush sooner. Heat is what boils wet fluid.
• Any brake hydraulic repair: a new caliper, hose or master cylinder is a good time to flush the whole system rather than bleed only the corner you opened.
• ATS-V on track: see the section below; the track fluid comes out before the car goes back to street duty.

ATS-V and track days: what GM says

For the 2016 and later ATS-V (and related V-Series and performance models), GM issued a service bulletin answering questions about high-temperature brake fluid for track use. The key points:

• For track use, owners may use any brand of brake fluid whose dry boiling point meets or exceeds 279 C (534 F). GM does not require a specific brand.
• Service intervals for that fluid should follow the fluid maker's recommendations, not the street schedule.
• The high-performance fluid should be flushed back out of the system when the car returns to road use.
• DOT 5 is not compatible with these vehicles.

The takeaway for a street-driven ATS-V is simple: stay on the factory-type fluid and schedule, and treat track fluid as a temporary swap that comes out when the season ends.

Symptoms of old or contaminated brake fluid

Old fluid rarely announces itself until it is hot. Watch for:

• A soft or sinking pedal after hard stops - water in the fluid can turn to vapor under heat. ADVICS describes this as vapor lock, where the brakes stop working properly because vapor compresses and fluid does not.
• Dark, cloudy fluid in the reservoir instead of clear-to-amber.
• A red brake warning light on the cluster, which can mean low fluid in the reservoir.
• Low reservoir level - the manual lists only two reasons: normal pad wear, or a leak that needs repair.

On the level itself, the ATS manual gives an instruction many owners miss: do not top off the brake/clutch fluid. As pads wear, the caliper pistons move out and the reservoir level drops a little; when new pads go in, the level comes right back up. Topping off a worn-pad system means fluid overflows at the next pad job. And if the level is low because of a leak, adding fluid does not fix it. Check the level with the car in Park on level ground; it should sit between the MIN and MAX marks.

How to flush the brake fluid on an ATS

A flush replaces all the old fluid, not just what is in the reservoir. The job is within reach of a careful home mechanic with a helper or a pressure bleeder.

1. Buy sealed, fresh GM-approved DOT 3 fluid. Plan on more than the reservoir holds, because you push fluid through all four corners and, on manual cars, the clutch circuit.
2. Siphon most of the old fluid out of the reservoir and refill with fresh fluid. Clean the cap and reservoir neck first so debris does not fall in.
3. Bleed each wheel in the order given in the service manual, pushing fluid through until it runs clean and bubble-free. Keep the reservoir from running low; letting it run dry pulls air into the master cylinder and ABS unit.
4. On manual-transmission cars, bleed the clutch circuit too, since it shares the reservoir.
5. Set the final level between MIN and MAX, tighten bleeder screws to the value in the factory service manual, and road-test at low speed before normal driving.

If the master cylinder or ABS unit was run dry or replaced, the factory service procedure may call for a scan-tool bleed of the ABS modulator. That part of the job is best left to a shop with the right tool. Brake fluid also strips paint, so wipe up spills on the body immediately, and do not overfill: the manual warns that spilled fluid can burn on a hot engine.

What to replace at the same time

A fluid flush is the right moment to look at the rest of the system, since the wheels are already off:

• Pads and rotors: if the pads are near the end, replace them first and flush after, so the reservoir level sets correctly on new pads. We carry a 2013-2018 Cadillac ATS front and rear brake kit for base-brake cars, plus individual brake pads and brake rotors.
• Rubber brake hoses: cracked or swollen hoses let moisture in and cause a soft pedal. See our brake hoses and brake lines.
• Seized bleeders or leaking calipers: if a bleeder snaps or a piston seal weeps, replace the caliper. Browse brake calipers.
• Master cylinder: a pedal that slowly sinks under steady pressure with no external leak points to internal bypass. See master cylinders.

Frequently Asked Questions

Can I use DOT 4 instead of DOT 3 in my Cadillac ATS?

The owner's manual specifies GM-approved DOT 3. DOT 4 is also glycol based, and GM's track-fluid bulletin for V-Series cars lists it alongside DOT 3 as a standard grade. For a street car, DOT 3 matches the factory spec; if you choose DOT 4, flush the whole system rather than topping up with it.

Can I use DOT 5 brake fluid in an ATS?

No. DOT 5 is silicone based, and GM states it is not compatible with these brake systems.

How often should I change brake fluid on a 2013-2018 ATS?

GM's schedule calls for it at the listed mileage or every 3 years, whichever comes first. Flush sooner if you tow, drive in the mountains or run the car on track.

My brake fluid level is a little low. Should I add some?

Not automatically. The manual says not to top off the brake/clutch fluid. A slight drop is normal pad wear; a larger drop means a leak that has to be found and repaired.

What fluid should I use for ATS-V track days?

GM allows any brand with a dry boiling point of at least 279 C (534 F), changed on the fluid maker's schedule, and flushed back out before returning to street use.

Does the clutch use the same fluid?

Yes. On manual-transmission ATS models the manual calls it the brake/clutch reservoir, so the clutch runs on the same DOT 3 fluid and should be bled during a flush.

Sources

1. GM - 2016 Cadillac ATS Sedan Maintenance Schedule - change brake fluid or every 3 years, whichever occurs first
2. GM - 2015 Cadillac ATS Sedan Maintenance Schedule - same 3-year brake fluid interval
3. Cadillac ATS Owner's Manual, Brake Fluid page - GM-approved DOT 3, shared brake/clutch reservoir, do not top off, level checks
4. GM Service Bulletin PIC6162D (ATS-V / CTS-V track fluid) - 534 F dry boiling point for track use, flush out for street, DOT 5 not compatible
5. 49 CFR 571.116 (FMVSS 116), Cornell LII - DOT 3, DOT 4 and DOT 5 minimum dry and wet boiling points; DOT 5 is silicone based
6. ADVICS - Brake Fluid Boiling Points - 3.7 percent water saturation, DOT 3 about one year, vapor lock