2012-2016 Audi A5 Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2012-2016 Audi A5 uses DOT 4 brake fluid, and Audi's scheduled maintenance calls for replacing it every 2 years regardless of mileage. For the best ABS and stability-control response, use a low-viscosity DOT 4 that meets the Volkswagen/Audi VW 501 14 specification, and flush the whole system rather than just topping up the reservoir.

Below is what the fluid does in your A5, why the 2-year interval exists even on a car that sits in the garage, how to tell your fluid is overdue, and what to check while the car is on the lift.

What Brake Fluid the 2012-2016 Audi A5 Takes

The A5 owner's manual is direct about it: use only the genuine brake fluid specified by the factory, and the grade Audi approves is DOT 4. It also says the fluid must be fresh and unused, which rules out pouring in the half-empty bottle that has been open on a shelf for a year.

DOT 4 is a federal grade defined in FMVSS 116. That standard sets minimum boiling points and a maximum cold-temperature viscosity, so any fluid labeled DOT 4 has to clear these numbers:

The "wet" number is the boiling point after the fluid has absorbed moisture, and that is the number that matters on a car a few years into its fluid change.

Why low-viscosity DOT 4 matters on an Audi

Volkswagen and Audi publish their own brake fluid standard, VW 501 14. Fluids that carry it are low-viscosity DOT 4 formulations, typically labeled "DOT 4 LV" or ISO 4925 Class 6, with a cold viscosity limit of 750 mm2/s instead of the 1,800 mm2/s that plain DOT 4 is allowed. Fluid makers position these for cars with ESP and traction control, which is exactly what the A5 has.

The reason is the ABS and stability-control hydraulic unit. That unit has a pump and a set of small solenoid valves that pulse fluid at high pressure when ABS or ESC steps in. Technical trade coverage of the topic notes that pressures inside the hydraulic control unit can exceed 3,000 psi, and that thicker fluid can cavitate as it is forced through those passages. Thinner fluid moves through the valves faster, especially in cold weather, so the system reacts the way it was calibrated to.

Low-viscosity DOT 4 that meets the same specifications is designed to mix safely with regular DOT 3 and DOT 4 glycol fluids, so a top-up is not a disaster. The goal on a flush is still to fill the whole system with the correct VW 501 14 fluid. Never put DOT 5 silicone fluid in an A5; it is a different chemistry and does not belong in a system designed for glycol-based DOT 4.

Flush Interval: Every 2 Years, Regardless of Mileage

Audi's 2014 model-year scheduled maintenance chart, which covers the A5 and S5 along with the rest of the lineup, lists "Brake Fluid - replace every 2 years regardless of mileage." The same chart has the brake system inspected for damage, leaks, pad thickness and fluid level at the regular service visits.

The time-based interval surprises owners who drive very little. The owner's manual explains why it exists: brake fluid gradually absorbs moisture from the air. As water content rises, it causes corrosion inside the brake system and lowers the fluid's boiling point. The manual warns that heavy braking with old fluid can cause vapor lock, which seriously reduces braking ability. Moisture gets in through hoses, seals and the reservoir vent whether the car is driven or parked, so the clock runs either way.

If you do not know when the fluid was last changed on a used A5, treat it as due. Many cars in this generation are now on second or third owners, and brake fluid is one of the services that gets skipped when a car leaves dealer maintenance.

Signs Your A5's Brake Fluid Is Overdue

• Dark fluid in the reservoir. Fresh DOT 4 is pale amber. Dark brown fluid has picked up moisture and debris.
• A pedal that goes soft after repeated hard stops. Mountain descents or spirited driving heat the fluid; if it has absorbed water, it can boil and the pedal gets long and spongy until it cools.
• Low fluid level or a brake warning light. The level drops slowly as pads wear, but a sudden drop points to a leak at a caliper, hose or line that needs attention before a flush.
• No record of a flush in 2 or more years. Moisture content cannot be judged by looking, so the service history is the best indicator. A shop can also test the fluid with a moisture or boiling-point tester.

Low fluid is a symptom, not a fix. If the reservoir keeps dropping, look at the pads first: worn pads push the caliper pistons out further and pull fluid from the reservoir. If you top off to make up for pad wear, the reservoir can overflow when new pads push the pistons back.

How the Flush Is Done and How Hard It Is

A proper flush pushes fresh fluid through all four brake circuits until clean fluid comes out of each bleeder. The general sequence is:

1. Remove as much old fluid from the reservoir as you can and refill with fresh VW 501 14 DOT 4 from a sealed container.
2. Bleed each caliper in turn, usually starting farthest from the master cylinder, until the fluid runs clear and bubble-free.
3. Keep the reservoir from running low at any point, which would draw air into the master cylinder and ABS unit.
4. Tighten each bleeder to the value in the factory service manual, set the level to the MAX mark, and road-test with a firm pedal before normal driving.

A pressure bleeder makes this a one-person job and is the method most European-car shops use. Two-person pedal bleeding works too. If air ever gets into the ABS hydraulic unit, for example from a run-dry reservoir or a replaced master cylinder, it may need a scan-tool-activated bleed procedure. That is where DIY owners most often get stuck.

For a home mechanic with basic tools, a routine flush is a moderate job of an hour or two. Two cautions from the owner's manual: brake fluid is poisonous and should stay sealed and out of reach of children, and it will damage paint on contact, so cover the fenders and wipe up spills with water immediately.

What to Check at the Same Time

A fluid flush has the wheels off and the calipers in reach, so it is the right time to look at everything else in the system:

• Pads and rotors. Audi's schedule calls for checking pad thickness and disc thickness. If the pads are close to their limit, doing brake pads for your A5 and the flush together saves a second bleed. Worn or grooved discs are replaced with matching brake rotors.
• Performance pads for harder driving. Owners who drive hard often move to a performance pad; for the 2013 A5 quattro we carry the Hawk HPS 5.0 front pad set. Confirm pad fitment by your car's brake option before ordering, since the A5 was built with different brake packages.
• Hoses and lines. Look for cracks, bulges and seepage at the rubber hoses near each wheel. Replacement brake hoses are cheap insurance on an older car.
• Caliper slide pins and hardware. Stuck slides cause uneven pad wear. Fresh brake hardware kits go on with new pads.

Frequently Asked Questions

Can I use DOT 3 in my 2012-2016 Audi A5?

No. Audi approves DOT 4 for the A5. DOT 3 has lower minimum dry and wet boiling points and does not meet the low-viscosity VW 501 14 specification. Use a DOT 4 LV fluid that lists VW 501 14.

Is DOT 5.1 acceptable?

Audi specifies DOT 4. DOT 5.1 is glycol-based and compatible in chemistry, but for an A5 the correct choice is a DOT 4 fluid that carries VW 501 14. Stay with the specified grade.

My A5 only has 15,000 miles. Does it really need a flush at 2 years?

Yes. Audi's schedule says every 2 years regardless of mileage, because the fluid absorbs moisture over time whether or not the car is driven.

Can I just top off the reservoir instead of flushing?

Topping off only adds fresh fluid to the reservoir; the moisture-laden fluid in the calipers, lines and ABS unit stays put. The owner's manual calls for periodic replacement, which means a full flush.

How much fluid does a flush take?

Plan on buying more than the reservoir holds, since you are pushing fluid through four calipers until it runs clean. Check your service information for the system capacity and buy sealed bottles; do not reuse fluid from an opened container that has been sitting.

Should I change brake fluid when I replace pads?

If the fluid is near or past its 2-year date, yes. The wheels are already off, and bleeding with new pads installed avoids a second trip. Shop brake parts for the rest of the job.

Sources

1. Audi A5 Owner's Manual - Changing brake fluid - DOT 4 approved by Audi, fresh fluid only, moisture absorption, vapor lock, toxicity and paint warnings
2. Audi 2014 MY Scheduled Maintenance Intervals (NHTSA) - brake fluid replace every 2 years regardless of mileage; brake system and disc checks
3. 49 CFR 571.116 (FMVSS 116) - Motor vehicle brake fluids - DOT 3/4 dry and wet boiling points and -40 viscosity limits
4. RAVENOL DOT 4 LV product data - VW 501 14, ISO 4925 Class 6, 750 cSt at -40 C, ESP use, miscibility
5. Tomorrow's Technician - Differences in Brake Fluid Matter - HCU pressures over 3,000 psi, cavitation, low-viscosity DOT 4