Brake and Clutch Fluid

Honda's full wording is worth having in front of you: "Always use Honda Heavy Duty Brake Fluid DOT 3. If it is not available, you should use only DOT 3 or DOT 4 fluid, from a sealed container, as a temporary replacement." So DOT 3 is the specification and DOT 4 is a temporary substitute, not an equal alternative.

Honda also warns explicitly that DOT 5 is not compatible with this braking system and can cause extensive damage. DOT 5 is silicone based and is a different product from DOT 5.1, which is glycol based; the labels are confusingly similar.

Honda does not publish a brake system capacity. The owner's manuals only tell you to keep the reservoirs between MIN and MAX. Owners report that a complete flush of the brakes and the clutch takes well under a quart, so one 32 oz bottle of DOT 3 covers the job with some left for top ups.

The clutch has its own reservoir. It uses the same fluid specification as the brakes, which is where the common belief that they share a reservoir comes from, but Honda lists a dedicated clutch fluid tank (46972-SF1-003) with its own cap and mounting band, sitting near the brake master cylinder. Check and bleed it separately. The clutch master and slave cylinders are a well known failure point on these cars, and a leaking master is often the reason a car will not go into gear.

Brake fluid absorbs moisture from the air whether you drive the car or not, which is why the interval is time based rather than mileage based. Track use calls for a higher boiling point fluid and more frequent flushes.