The replacement cycle of brake oil is usually determined according to the time. Most automobiles require replacement once every two years, but there is no special requirement for mileage. If we want to know more accurately whether the brake oil needs to be replaced, the best way is to test the moisture content of the brake oil. If this value exceeds 3%, we suggest replacing it; if the moisture content exceeds 5%, it must be replaced.

Normally, the moisture content of brake oil is less than 1%. If it is too high, the boiling point of brake oil will be lowered, which will lead to boiling vaporization of brake oil and brake failure in high-strength braking of automobiles. Experiments show that when the water content of brake oil reaches 3%, the boiling point of brake oil will be reduced by 25%. If the water content of brake oil reaches 7-8%, the boiling point of brake oil will be reduced by more than 50%. For example, the dry boiling point of some brake oil is 210 C. When the water content exceeds 3%, the boiling point has been reduced to 152 C. If the water content of the brake oil reaches 7-8%, the boiling point may have been reduced to about 100 C.

How long will the water content of brake oil exceed the standard? Experiments show that when a new car runs for 12 months, its brake oil may inhale about 2% of the water; when it runs for 18 months, the water content can reach 3%; when it runs for more than five years, the water content of the brake oil will reach 7-8%. If the water content is more than 3%, we suggest replacing it. This is also the reason why many automobile manufacturers stipulate that brake oil should be replaced once every two years.

Of course, you can also appropriately extend or shorten the replacement cycle according to the local environment and personal use conditions. If the local climate is dry and personal driving is not intense, it is no problem to replace the brake oil for three or four years; if the local climate is very humid or often wading, it is recommended to shorten the replacement cycle properly, preferably once a year.