2013-2018 Audi RS6 Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2013-2018 Audi RS6 (C7) uses a low-viscosity DOT 4 brake fluid of the type built to the Volkswagen Group standard VW 501 14, and Audi's published maintenance schedule calls for a brake fluid change every 2 years on all vehicles, with no mileage trigger. If your RS6 has gone two years since its last flush, it is due regardless of how few miles it has covered.

Below is what that fluid spec means, why the interval is time-based, how to tell the fluid is tired, and what a proper flush on this car involves.

What Brake Fluid the C7 RS6 Uses

The C7 RS6 and its RS7 sibling share the same brake hardware family, and like the rest of the VW Group lineup of that era they are filled from the factory with a glycol-based DOT 4 fluid formulated for low viscosity. The Volkswagen Group writes that requirement as VW 501 14. Fluids sold against that standard, such as the DOT 4 LV products that list VW 501 14 on the label, are built to ISO 4925 Class 6, which caps cold viscosity at 750 mm2/s at minus 40 degrees, well below the ceiling a plain DOT 4 fluid is allowed.

Why does that matter on an RS6? The car's ABS, stability control and traction control all work by rapidly moving fluid through the hydraulic unit. Thin fluid moves faster through those small valves and passages, especially on a cold morning, so the electronics can build and release pressure the way they were calibrated to. A generic DOT 4 fluid will stop the car, but it is not what the system was designed around. Always confirm the exact specification in your owner's manual before buying fluid.

The "wet" boiling point is the federal test figure for fluid that has absorbed moisture. Notice how far it sits below the dry figure. That gap is the entire reason the fluid has a change interval.

Why Audi Says Every 2 Years, Not Every X Miles

Audi of America's maintenance schedule lists "Brake fluid - Change" at "Every 2 years" for "All vehicles." It is the only brake item on that schedule set purely by time. Pad thickness is checked at every minor service and hoses at every standard service, but the fluid is replaced on the calendar.

The reason is chemistry. Glycol-based brake fluid is hygroscopic: it pulls moisture out of the air through the reservoir vent, hose walls and seals whether the car is driven or parked. Brembo describes how that absorbed humidity turns to vapor long before the boiling point printed on the bottle is reached, causing longer pedal travel and a slower, weaker brake response. Brembo's own general guidance is replacement every 2 to 3 years, deferring to the vehicle maker's schedule, which on this car is 2 years.

A low-mileage RS6 that sits in a garage most of the year still needs the flush. If anything, a car that is stored and then driven hard on a warm day is exactly where old fluid bites.

Signs Your RS6 Brake Fluid Is Overdue

• Soft or long pedal after hard use. A pedal that is firm around town but sinks after a spirited run or a long downhill points to moisture-laden fluid boiling in the calipers.
• Dark fluid in the reservoir. Fresh fluid is clear to light amber. Dark brown fluid has aged and picked up contamination, though color alone is not a reliable moisture test.
• Brake fluid warning or low level. A falling level usually means the pads have worn and the caliper pistons have moved out, but it can also mean a leak. Check the pads before you top up.
• ABS or stability control faults. Old, contaminated fluid is hard on the hydraulic unit's valves. Any warning light needs a proper scan, not just a flush.
• No record of the last change. On a used RS6 with no paperwork, treat the fluid as due.

A test strip or electronic tester can give a rough moisture reading, but the calendar is the rule Audi uses.

How a Proper Flush Works on This Car

A flush replaces all of the old fluid in the system, not just what is in the reservoir. On the RS6 the work goes like this:

1. Remove as much old fluid from the reservoir as practical and refill with fresh, sealed low-viscosity DOT 4 fluid of the correct specification.
2. Bleed each caliper in the order given in the factory service information, pushing fresh fluid through until it runs clean and bubble-free at every bleeder.
3. Keep the reservoir from running low during the process so no air enters the lines.
4. On cars with the ABS/ESC hydraulic unit, follow the factory procedure; some jobs call for a scan tool to cycle the unit's valves so old fluid trapped inside is also flushed.
5. Set the level between the reservoir marks, confirm a firm pedal with the engine off and running, and road test at low speed before driving normally.

Use fluid from a freshly opened container. An opened bottle on a shelf has already started absorbing moisture. Brembo also notes brake fluid is corrosive, so protect the paint around the reservoir and wipe spills right away.

A pressure bleeder and a helper make the job straightforward for a confident home mechanic. If the ABS unit needs to be cycled with a scan tool, or you have any doubt about getting air out of the system, have a shop do it. There is no margin for error on a car this fast.

What to Check or Replace at the Same Time

A fluid flush has the wheels off and the brakes exposed, so it is the natural time to look at the rest of the system:

• Pads. Measure remaining thickness on both axles. Shop brake pads if you are close to the wear limit.
• Rotors. Check thickness against the minimum stamped on the rotor and look for heat cracks and a lip at the outer edge. For steel-rotor cars, see our GiroDisc slotted front rotors for the 2013-2018 RS6 and RS7 C7, which are made for the standard steel brakes and do not fit the carbon ceramic option. Browse more brake rotors here.
• Hoses and lines. Audi's standard service already includes checking brake hose condition. Cracked or swollen hoses should be replaced before the flush, not after. See brake hoses and brake lines.
• Bleeder caps. Audi's schedule specifically calls for checking that the bleeder caps are present. Missing caps let dirt and moisture into the bleeder threads.

Know which brake package your car has before ordering parts. The C7 RS6 was offered with steel rotors as standard and carbon ceramic rotors as an option, and the two do not share rotors or pads.

Frequently Asked Questions

Can I use regular DOT 4 in my 2013-2018 Audi RS6?

Standard DOT 4 is chemically compatible, but it is thicker when cold than the low-viscosity VW 501 14 type fluid the car was designed around. For correct ABS and stability control behavior, use a DOT 4 LV fluid that lists VW 501 14 and confirm it against your owner's manual.

Is DOT 5 silicone fluid safe for the RS6?

No. DOT 5 is silicone-based and does not mix with the glycol-based fluid in this system. Stick with the glycol-based DOT 4 low-viscosity type specified for the car.

My RS6 has very low miles. Do I still need to change the fluid every 2 years?

Yes. Audi's schedule sets brake fluid at every 2 years for all vehicles with no mileage condition, because the fluid absorbs moisture over time whether the car is driven or not.

Does the carbon ceramic brake option use a different fluid?

The fluid requirement comes from the car's hydraulic and stability control system, not the rotor material, so the same low-viscosity DOT 4 specification applies. The pads and rotors, however, are completely different between steel and carbon ceramic cars.

Should I use a higher boiling point racing fluid for track days?

Some owners do, but many racing fluids are not built to the low-viscosity standard, and they usually need changing far more often. For a street-driven RS6, the correct-spec fluid changed on schedule, plus a fresh flush before any track event, is the safer plan.

Sources

1. Audi of America, 2018 Audi Maintenance Schedule - All Models (NHTSA) - brake fluid change every 2 years for all vehicles; pad, hose and bleeder cap checks
2. 49 CFR 571.116, FMVSS No. 116 Motor Vehicle Brake Fluids (Cornell LII) - DOT 3 and DOT 4 dry and wet boiling points and cold viscosity limits
3. RAVENOL USA, VW 501 14 specification - DOT 4 LV fluid for VW 501 14 conforms to ISO 4925 Class 6, max 750 cSt low-temperature viscosity
4. Brembo, Brake fluid: when changing it saves the whole team - hygroscopic fluid, vapor lock, 2 to 3 year general replacement guidance, corrosive to paint