In the disc type brake systems of most vehicles, DOT 4 brake fluid is poured - one of the most popular and common among analogues. The main differences between such agents are considered to be the boiling point, composition and ability to absorb moisture vapor. The DOT 4 category is considered the highest quality and most versatile. Compared to DOT 3, it absorbs many times less water and keeps the boiling point unchanged for a long time. Such features of the composition can extend its term of use.
Types of brake fluids
The DOT brake system was formulated by the US Department of Transportation. FMVSS safety standards were used as the basis for creating these standards. In translation, the abbreviation DOT stands for "Department of Transportation Security." The moisture-binding substances included in the composition are indicated by the number 4. Such agents do not pass certification according to GOST.
Since DOT 4 is not considered a product of oil refining, its markings are corresponding - an octagonal yellow shape, bordered by a black line. In the center of the figure is a diagram of the brake system. A similar symbol, diagonally crossed out, indicates that such a composition cannot be poured into the system.
The boiling point and viscosity of a dry and moisture-filled liquid are the criteria by which brake compounds are divided into types. Polyglycols are considered the basic basis of DOT 3 and DOT 4, but DOT 5 is created on the basis of silicone, which is why these categories are not mixed together. The same substances are used to create liquids of the DOT 3 and DOT 4 categories, so they can be mixed and interchanged.
Marking and composition of brake fluids DOT 4
DOT 4 brake fluid in its base contains linear polyethers and polyalkylene glycols. In most cases, the production of such compositions uses polyethylene glycol, but on the packaging it is often indicated under a different name, since various additives and liquid polymers are taken into account.
Unlike the predecessor DOT 3, the liquid DOT 4 contains special additives in its composition - for example, borates. They bind water entering the material from the air during operation.
Sports cars use DOT 5.1 brake fluids, obtained by adding special additives and additives to a DOT 4 standard fluid.
DOT 4 Brake Fluid Compatibility
For many motorists, one of the most pressing and burning issues remains the compatibility of brake fluids of different classes and categories. Specialists, as a rule, advise using compounds of well-known brands - such as Castrol brake fluid or Bosch DOT 4 brake fluid. Be sure to observe the marking of the composition.
The Russian automotive market has a huge number of different brake fluids. They are not advised to mix with each other, however, in emergency cases this can be done, but it is advisable to be guided by certain rules.
DOT 4 brake fluid can be mixed with analogues like DOT 3, DOT 4.5, DOT 5.1. Diluting it with silicone-based agents such as DOT 5 and DOT 5.1 (ABS) is prohibited.
DOT 4 brake fluid - characteristics
The main physico-chemical parameters of the compositions that affect their quality are:
- viscosity;
- boiling temperature;
- the ability to absorb moisture vapor;
- resistance to corrosion.
According to the requirements for the standard of DOT 4 fluids, their boiling point should not be lower than 250 ° C. This indicator can be reduced to 165 ° C for those liquids that absorb moisture from the environment in a total amount of 3.5%.
Fluid viscosity is measured with a viscometer. This parameter must not exceed 750 mm 2 / s. In practice, only viscosity is one of the main properties, while the density of the brake fluid is almost never taken into account.
The corrosion resistance of DOT 4 is directly dependent on its acidity level. A normal value is in the range of pH 7.0-11.5 units.
Brake fluid life
Depending on the additives and additives, hygroscopicity and operating conditions, the service life of the agent may vary. For example, low-quality parts of the brake system can change the characteristics of the brake fluid, which affects its functions and working life. For this reason, the brake fluid is changed every 2-2.5 years.
Why exactly DOT 4?
DOT 4 brake fluid has the following advantages, due to which it is one of the most popular in the world:
- reliability;
- reasonable prices;
- wide range of temperatures at which it can be used.
The expensive DOT 5.1 is practically not used by motorists, because it costs more, but in its functionality it is no different from DOT 4. Tests conducted by experts and amateurs show that DOT 4 brake fluid is the gold standard. Reviews left on the composition confirm its reliability and high quality, coupled with an acceptable cost.
Boiling temperature
The kinetic energy of the car during braking is transformed into heat. The pads, heating up, transfer it to the pistons and caliper body, which is already heated by brake fluid. Based on this, the first requirement is put forward for it: a high boiling point, which will avoid the “failure” of the brake pedal. The high speed mode of modern cars has led to the fact that the old types of such compounds ceased to cope with their functions, and they were replaced by DOT 4 brake fluid. Toyota, one of the most respected automobile concerns in the world, advises using such compositions.
Corrosion resistance
The second requirement is minimal corrosion activity. Oxidation of the piston metal is not the worst thing that can happen; corrosion of brake lines is much more dangerous. Ensuring a high boiling point of the brake fluid became possible only through the use of a polyethylene glycol base, which is characterized by a high level of hygroscopicity. Because of this, DOT 4 formulations are only stored in tightly closed containers. The fluid that has accumulated a large amount of water not only accelerates the corrosion processes in the brake system, but also boils at a much lower temperature. This is often found in motorcycles and sports cars: "failures" of the brakes during aggressive and fast driving can cause a serious accident.
Lubricating properties
Good lubricating properties are the third requirement for brake fluids. These characteristics help reduce wear on both the ABS valve body and the brake cylinder linings. The DOT 4 standard in these parameters is slightly inferior to the new DOT 5, while the latter has a higher boiling point and lower hygroscopicity, which allows it to be used for fast driving. DOT 5.1 fluids were developed for vehicles equipped with anti-lock braking systems. This implies the introduction of a small amount of antifriction additives into the glycol base . For most vehicles, it is desirable to use liquids of this particular class, since they are compatible with seals that are designed for previous fluid standards.
High viscosity
High viscosity is the fourth requirement for brake fluids. Preserving the viscosity of the fluid allows the brake system to operate normally at any ambient temperature. This parameter is most important for vehicles with ABS. After all, solidification of the liquid can cause the failure of the valve body on those cars on which the course stabilization is tied to an anti-lock system. Modern crossovers can also be attributed to this: failures in the traction distribution system will cause poor vehicle handling.
Mobil Brake Fluid
The composition is recommended by the manufacturer for use in drum, disc and traction control systems installed on medium-power vehicles.
The Mobil DOT 4 brake fluid is used in accordance with the following recommendations:
- It is poured only in concentrated form from a new package or tightly closed.
- Immediately after use, the bottle should be tightly closed, since the composition quickly absorbs moisture from the environment, which negatively affects its operational life.
- The drained brake fluid cannot be reused.
- Spilled compound is immediately removed, as the paintwork of the body can corrode.
- The brake fluid is replaced every two years or every 40 thousand kilometers.
- Fully compliant with DOT 4 standards and can be used for ABS systems.
- Can be mixed with brake fluids of categories DOT 4 and DOT 3.
Castrol brake fluid
Despite the fact that Castrol DOT 4 brake fluid is certified according to the DOT 4 standard, its boiling point exceeds the requirements and is 265 ° C, with water ingress - 175 ° C. According to the manufacturer's recommendations, it must be changed every two years, respectively, it can be poured into sports cars.
Castrol DOT 4 brake fluid is sold in a very inconvenient packaging: it is impossible to find a 1 liter bottle in automobile stores. For this reason, when replacing the liquid, you will have to buy several half-liter containers, overpaying for packaging. This is noted by many car owners.
The advantages of this brake fluid:
- Resistance to boiling even when moisture enters the composition.
- Compliance with more stringent standards.
- Ideal for cars with ABS - has good viscosity properties.
Brake fluid "Dew"
Rosa DOT 4 brake fluid is a mixture of anticorrosive and antioxidant additives and a boron-containing polyester. It differs in good boiling points in dry and wet form - 260 ° C and 165 ° C, respectively. It can be operated at ambient temperature in the range from -40 to +45 .
The Rosa DOT 4 brake fluid is used in brake systems of passenger cars and trucks, including front-wheel drive cars of domestic production.
The life of the fluid is three years. It can be mixed with such compounds as Neva and Tom without loss of performance.
Sintec Brake Fluid
Perhaps one of the most affordable in terms of price (only 100 r) brake fluids of domestic production. Super DOT 4 brake fluid is manufactured at the Obninskorgsintez plant. Despite domestic production, in terms of its characteristics, it can overtake many imported analogues: the boiling point is 240 ° C in dry form and 155 ° C in wet form. Ideal for measured trips, a slight difference in viscosity during the ride is not felt.
The only disadvantage is unstable characteristics: all the tests that brake fluid passed from Obninsk showed different results. Of course, this does not affect the requirements of the standard, but it does not say anything good about the manufacturer.
Liqui Moly Brake Fluid
Liqui Moly brake fluid loses its analogues in its characteristics: the boiling point for the dry and wet versions is 230 ° C and 155 ° C, respectively, at a low temperature the viscosity is 1800 mm 2 / s. The composition characteristics ideally comply with the DOT 4 standards, but do not exceed them. Affordable price 300 r. this compensates to a certain extent, however, it is definitely not worth using such a liquid in our climate for cars with ABS.
Separately, it is worth noting the excellent lubricating and anti-corrosion properties of Liqui Moly, on which the manufacturer emphasized. By its property, this brake fluid is ideal for drivers who prefer a quiet rhythm of driving and living in the middle lane of our country.
Benefits of Liqui Moly Brake Fluid:
- Excellent anti-corrosion properties.
- Protection for brake hoses and rubber seals.
Brake fluid selection
A suitable brake fluid is selected according to the vehicle parameters. You can find out exactly which composition was filled at the factory, and which can be used in the future, in the manual for the repair and operation of a car. You can also ask your authorized dealer.
It is worth paying attention to such brake fluid parameters as boiling point in dry and wet form, viscosity and standard. The categories below DOT 4 cannot be used for vehicles equipped with anti-lock braking systems, as this can damage both the ABS itself and the braking system.
You can contact the service station with an authorized dealer to diagnose the system and fill in new brake fluid.