2015-2020 Honda FIT Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2015-2020 Honda Fit is specified for Honda Heavy Duty Brake Fluid DOT 3. If that exact fluid is not available, Honda allows DOT 3 or DOT 4 from a sealed container as a temporary substitute, and it says DOT 5 must never go in. Honda's own maintenance schedule says to replace the brake fluid every 3 years, regardless of what the Maintenance Minder shows.

Below is what that spec means, why the 3-year clock matters on a small commuter car, how to tell your fluid is tired, and what to look at while the system is open.

What Brake Fluid the 2015-2020 Fit Takes

The Fit owner's manual lists one fluid for both the brake system and, on manual-transmission cars, the hydraulic clutch: Honda Heavy Duty Brake Fluid DOT 3. The manual adds three points every owner should know:

• DOT 3 or DOT 4 is a stopgap only. If the Honda fluid is not on hand, a DOT 3 or DOT 4 fluid from a sealed container can be used temporarily.
• Honda wants its own fluid back in. The manual warns that non-Honda brake fluid can cause corrosion and shorten system life, and recommends having the system flushed and refilled with the Honda fluid as soon as possible.
• Never DOT 5. Fluid marked DOT 5 (silicone based) is not compatible with the Fit's brake system and can cause extensive damage.

The fluid level should sit between the MIN and MAX marks on the side of the reservoir. If it has dropped to or below MIN, Honda says to have the car inspected for leaks or worn parts rather than simply topping it off.

DOT 3 vs DOT 4 vs DOT 5 at a glance

The DOT grades are set by federal standard FMVSS 116, which defines minimum boiling points for new (dry) fluid and for fluid that has absorbed water (wet):

Notice how far each fluid's boiling point falls once it is wet. That drop is the whole reason brake fluid has a replacement interval.

How Often to Flush It: Honda's 3-Year Rule

The Fit uses Honda's Maintenance Minder, which shows service codes on the dash when engine oil and other items are due. Brake fluid is the exception you cannot leave entirely to the Minder. Honda's Fit Maintenance Minder literature states that, independent of the Maintenance Minder information, the brake fluid should be replaced every 3 years.

In practice that means:

• If the Minder calls for brake fluid, do it then.
• If it has been 3 years since the last fluid change and the Minder has not asked, do it anyway.
• A low-mileage Fit still needs it. Moisture gets into fluid with time, not miles, so a garage-kept car that only goes to the grocery store is on the same 3-year clock.

For a 2015 model that has never had a brake fluid change, the fluid is long overdue. Buyers of a used Fit should assume the fluid has not been done unless there is a receipt.

Why Old Brake Fluid Is a Problem

DOT 3 and DOT 4 are glycol-based and absorb water. Brembo explains that fluid picks up moisture from the air through the porosity of the brake lines, and that the boiling point of a 3-year-old fluid can be significantly lower than new fluid. The FMVSS 116 numbers in the table show the scale of that loss: a DOT 3 fluid's required minimum drops from 205 C dry to 140 C wet.

When the fluid gets hot enough to boil, it forms vapor bubbles. Brembo describes this vapor lock as a loss of hydraulic pressure and reduced braking. Vapor compresses where liquid does not, so the pedal goes soft or sinks. Water in the fluid also promotes internal corrosion in the parts Honda calls out in its warning: caliper bores, wheel cylinders, the master cylinder, and the ABS modulator.

On a Fit, the situations that heat the fluid most are long mountain descents with a full load, repeated hard stops in traffic, and summer heat. The front brakes do most of the work and get the hottest.

Signs the Fluid Needs Attention

• Dark fluid. Fresh DOT 3 is clear to light amber. Brown or dark fluid in the reservoir has been in service a long time.
• Soft or sinking pedal, especially after repeated stops or a long downhill, points to air, moisture, or a leak.
• Level at or below MIN. Pads wearing down will lower the level slowly, but a drop usually means worn pads or a leak. Honda's advice is to have it inspected.
• Brake warning light on. On most cars this is tied to low reservoir level or the parking brake. Check the fluid before driving further.
• Clutch pedal feels different on a manual car. The clutch shares the reservoir fluid spec, so old fluid affects clutch hydraulics too.

How the Flush Is Done on a Fit

The 2015-2020 Fit has four-wheel ABS with ventilated front discs and rear drum brakes. Spec sheets list both a 6-speed manual and a CVT. That layout affects the flush in a few ways:

• Four bleeders, two types. The front calipers and the rear drum wheel cylinders each have a bleeder screw. Rear wheel cylinder bleeders are small and often seized; soak them with penetrant and use a six-point wrench.
• Keep the reservoir from running dry. Letting the reservoir empty pulls air into the master cylinder and ABS unit, which is much harder to bleed out. A standard two-person pedal bleed or a pressure bleeder works; follow the bleed sequence in the factory service manual.
• Manual transmission cars: the clutch slave line uses the same fluid. Flush it with the brakes so the whole system gets fresh fluid.
• Use new, sealed fluid. An opened bottle that has sat on a shelf has already been taking on moisture.
• Tighten bleeders and check the pedal before driving. Torque bleeder screws to the value in the factory service manual, top the reservoir to between MIN and MAX, and confirm a firm, high pedal with the engine running.

A home mechanic with basic tools can do a Fit brake flush in a driveway. If the pedal is still soft after bleeding, air may be trapped in the ABS modulator, and that calls for a shop with a scan tool that can cycle the ABS pump.

What to Replace While the System Is Open

A fluid flush is a good time to look at everything that the fluid touches and everything that wears with it:

• Front pads and rotors. Pull the wheels and measure pad thickness and rotor condition. If the pads are low, doing pads and rotors at the same visit saves a second bleed. Our 2015-2020 Honda Fit front brake kit pairs matched rotors and pads for this car.
• Calipers. A caliper that leaks at the bleeder or piston seal, or that drags, should be replaced rather than bled around. See our brake calipers.
• Rubber brake hoses. Look for cracks, bulges, or wet spots near the crimps. Replacement brake hoses are cheap insurance on an older Fit.
• Rear drums and shoes. With the drums off, check shoe lining and look for fluid seeping from the wheel cylinders. Browse brake shoes for the rear.
• Hardware. Worn clips and slide pins cause noise and uneven wear; a brake hardware kit refreshes them.

Frequently Asked Questions

Can I use DOT 4 in my 2015-2020 Honda Fit?

Honda allows DOT 4 from a sealed container as a temporary replacement when its Heavy Duty DOT 3 fluid is not available. Honda recommends having the system flushed and refilled with its own DOT 3 fluid as soon as possible after that.

How often should a Honda Fit have its brake fluid changed?

Every 3 years. Honda states this applies independent of the Maintenance Minder, so change it at 3 years even if the Minder has not called for it.

Is DOT 5 brake fluid safe in a Honda Fit?

No. Honda says fluid marked DOT 5 is not compatible with the Fit's brake system and can cause extensive damage.

Does the clutch on a manual Fit use brake fluid?

Yes. The owner's manual lists Honda Heavy Duty Brake Fluid DOT 3 for both the brake and clutch systems, so flush the clutch hydraulics at the same time.

My brake fluid is low. Should I just top it off?

Adding fluid to get it back between MIN and MAX is fine to get home, but Honda says a level at or below MIN should be inspected for leaks or worn brake parts. Worn pads lower the level gradually; a sudden drop means a leak.

Does a low-mileage Fit still need a brake fluid flush?

Yes. Brake fluid absorbs moisture over time through the hoses and seals whether the car is driven or not, which is why Honda's interval is based on years.

Sources

1. Honda Owners - Fit Maintenance Minder System - replace brake fluid every 3 years independent of the Maintenance Minder
2. Honda Fit Owner's Manual - Brake/Clutch Fluid - Honda Heavy Duty DOT 3 spec, DOT 4 temporary use, DOT 5 warning, MIN/MAX level guidance
3. 49 CFR 571.116 (FMVSS 116) - Motor vehicle brake fluids - dry and wet boiling point minimums for DOT 3, DOT 4 and DOT 5
4. CarsDirect - 2018 Honda Fit Specs - front disc/rear drum brakes, four-wheel ABS, 6-speed manual and CVT
5. Brembo - Brake Fluid for Cars - moisture absorption through brake lines, boiling point loss in 3-year-old fluid, vapor lock