2017-2019 Genesis G90 Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2017-2019 Genesis G90 uses hydraulic brake fluid that meets the DOT 3 or DOT 4 specification (FMVSS 116), and the system holds about 0.74 to 0.85 US quarts (0.7 to 0.8 liters). The factory maintenance schedule calls for the brake fluid to be inspected every 7,500 miles or 12 months rather than replaced at a fixed mileage, so the practical flush interval comes down to fluid condition and age. Here is what Genesis actually specifies, what the federal fluid standard means for your choice of DOT 3 or DOT 4, and how to tell when your G90 is due.

What Brake Fluid the Genesis G90 Takes

The Genesis G90 owner's manual lists brake fluid in its Recommended Lubricants and Capacities table as FMVSS116 DOT-3 or DOT-4, with a capacity of 0.74 to 0.85 US quarts (0.7 to 0.8 liters). The maintenance chapter repeats the same instruction: use only hydraulic brake fluid conforming to DOT 3 or DOT 4. Both are glycol-ether fluids, which is why the manual allows either one. DOT 5 silicone fluid is a different chemistry and is not on the list, so do not put it in a G90.

The spec is the same on both engines offered in these years, the 5.0-liter Tau V8 and the 3.3-liter Lambda twin-turbo V6. The capacity figure is the whole system; a proper flush pushes more fluid than that through the lines, so buy more than the capacity number suggests and use a fresh, sealed bottle.

DOT 3 vs DOT 4 in Your G90

The difference between the two grades is boiling point. The federal brake fluid standard, 49 CFR 571.116, sets minimum equilibrium reflux boiling points for each grade:

"Dry" is fresh fluid straight from a sealed container. "Wet" is the same fluid after it has absorbed moisture; ADVICS, an OE brake supplier, defines the wet boiling point as the fluid's boiling point after it has taken on 3.7 percent water by volume. Because the G90 is a heavy full-size sedan, it puts a lot of heat into its brakes on long downhill grades and repeated hard stops. DOT 4 gives you more margin against boiling, and it is the grade most brake techs reach for on a car like this. DOT 3 still meets the factory requirement if that is what you have.

Can you mix them? Both grades are glycol-based and the manual allows either, but the cleanest practice is to flush the system and refill with one fluid rather than topping off a reservoir of unknown fluid with a different grade. The one hard rule from the manual: never let mineral-based oil into the system. It says even a few drops of something like engine oil can damage brake system parts.

What the Factory Schedule Actually Says About Flushing

This is where G90 owners get conflicting answers. In the normal maintenance schedule printed in the owner's manual, the brake fluid line is marked "I" at every interval, which Genesis defines as inspect and, if necessary, adjust, correct, clean or replace. The inspection comes due every 7,500 miles or 12 months, whichever comes first. The schedule does not list a fixed replacement mileage for brake fluid, and the severe usage table (towing, mountain roads, short trips, dusty or salted roads) does not add one either; it tightens the intervals for pads, discs, calipers and the parking brake instead.

So the factory approach is condition-based: someone looks at the fluid every year and replaces it when it needs it. In practice, glycol fluid absorbs moisture from the air over time no matter how many miles you drive, which is why ADVICS advises replacing DOT 4 roughly every two years and following your owner's manual. A reasonable plan for a G90 is:

• Check the level and color at every 7,500-mile or 12-month service, as the manual requires.
• Have the fluid tested for moisture when the car is around two years or more past its last flush.
• Flush sooner if you tow, drive mountain roads, or see dark fluid or a soft pedal.
• Flush any time the hydraulic system is opened for a caliper, hose or master cylinder replacement.

Signs Your G90 Brake Fluid Needs Attention

Moisture-laden fluid rarely announces itself during normal commuting. It shows up when the brakes get hot, because the water in the fluid boils and forms vapor. Vapor compresses where liquid does not, which is how a pedal goes soft or sinks during a long descent. Watch for:

• Soft or spongy pedal, especially after repeated stops or a long downhill.
• Dark or discolored fluid in the reservoir. Fresh fluid is clear to light amber.
• Low fluid level. The manual notes the level falls slowly as the pads wear, which is normal. A level that drops quickly or needs frequent top-offs points to a leak.
• Red brake warning light with the parking brake released. On the G90 the Parking Brake and Brake Fluid warning light doubles as the low-fluid warning.

The manual is specific about that warning light. If it comes on with the parking brake released, pull over safely, check the fluid level with the engine off, and top up as needed. If you find a leak, if the light stays on, or if the brakes do not work properly, do not drive the car. If the ABS light and the brake warning light are on together, the manual warns the brake system will not work normally, so avoid hard braking and have the car inspected.

How to Check and Flush the Fluid

The brake fluid reservoir is in the engine compartment, with MIN and MAX marks on its side. The owner's manual procedure for checking and topping off:

1. Clean around the reservoir cap thoroughly before opening it so dirt does not fall into the fluid.
2. Check that the level sits between MIN and MAX.
3. If low, add the specified DOT 3 or DOT 4 fluid up to MAX.
4. Never use fluid from a container that has been left open for an extended time; the manual says its quality cannot be guaranteed.
5. Keep fluid off the paint, which it will damage, and out of your eyes. If fluid gets in your eyes, the manual says to flush them with clean water for at least 15 minutes and get medical attention.

A full flush means bleeding every caliper until clean fluid comes out, starting at the wheel farthest from the master cylinder and working closer. The G90 has ABS, stability control, an electronic parking brake and Auto Hold, so the hydraulic unit contains its own internal passages. A standard pressure or two-person bleed replaces the fluid in the lines and calipers; if air has gotten into the ABS unit, a shop may need a scan tool to cycle the valves during the bleed. Tighten bleeder screws to the value in the factory service manual rather than guessing.

Parts to Check While You Are In There

A fluid service is a good time to look over the rest of the system, since the factory schedule inspects these items at the same 7,500-mile intervals:

• Pads and rotors. The fluid level drops as pads wear, so a low reservoir may simply mean the pads are near the end. We carry 2017-2019 Genesis G90 front ceramic brake pads, and you can browse more brake pads and brake rotors.
• Hoses and lines. The manual calls for checking brake hoses and lines for chafing, cracks, deterioration and leaks. Replacements are in our brake hose and brake line collections.
• Calipers. Look for wetness around the piston boots and bleeders. A seeping caliper is a common reason a G90 needs frequent top-offs; see our brake calipers.

Frequently Asked Questions

Does the Genesis G90 use DOT 3 or DOT 4 brake fluid?

Either. The owner's manual specifies FMVSS 116 DOT 3 or DOT 4. DOT 4 has higher minimum boiling points under the federal standard, which gives a heavy car like the G90 more margin under hard braking.

How much brake fluid does a G90 hold?

The manual lists 0.74 to 0.85 US quarts (0.7 to 0.8 liters) for the system. A flush uses more than that because you push fluid through each caliper until it runs clean.

How often should I flush the brake fluid on a 2017-2019 G90?

Genesis schedules an inspection every 7,500 miles or 12 months and does not print a fixed replacement mileage. Because the fluid absorbs moisture with age, many shops test it and replace DOT 4 about every two years, sooner if you tow or drive in the mountains.

Can I use DOT 5 in my G90?

No. The manual only lists DOT 3 and DOT 4. DOT 5 is silicone-based and is not a substitute. Stick with the grades Genesis specifies.

Why is my G90 brake fluid level going down?

A slow drop is normal as the pads wear, according to the manual. If you need to add fluid often, the manual says that could indicate a leak, so have the calipers, hoses and lines inspected.

Sources

1. Genesis - 2018 G90 Owner's Manual - DOT 3/DOT 4 spec, 0.7-0.8 L capacity, 7,500 mi/12 month inspection schedule, severe usage table, warning light and fluid handling instructions
2. 49 CFR 571.116 (FMVSS 116) - Motor vehicle brake fluids - minimum dry and wet boiling points for DOT 3 and DOT 4, moisture labeling requirements
3. ADVICS Aftermarket - Brake Fluid Boiling Points - wet boiling point definition (3.7 percent water), vapor lock, DOT 4 replacement guidance