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5 Fluids you should check to keep your car running smoothly

Joel Ilton

Updated 18 Jan 2023

Joel Ilton

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Modern motor vehicles use a variety of lubricants and fluids to operate as they were designed. These fluids are used to lubricate, disperse heat and operate different functions during day-to-day driving. On most vehicles, these fluids need to be replaced at certain intervals, to keep the vehicle operating in peak condition.

1. Engine Oil

The main lubricant vehicles use is engine oil. This oil provides proper lubrication of all the moving parts inside an internal combustion engine - to disperse heat and prolong the life of all components.

It is essentially the lifeblood of the engine, and without it serious damage can be caused in a very short amount of time.

There are also cleaning properties built into modern engine oils that prevent blockages and contaminants from restricting oil flow.

It’s important to replace your engine oil at regular intervals, as oil breaks down and loses these properties over time.

It is also important to use the correct grade and specification of oil in your engine.

Many modern European and diesel engines require certain additives which are present only in specific oil grades, and using the wrong specification can cause major and expensive engine and component damage.

The normal service interval can vary between 10,000km to 20,000km, depending on the vehicle, but may need to be changed more frequently if the vehicle is operated under abnormal conditions ie. 4wding, towing, racing, excessive stop-start driving.

2. Brake Fluid

Modern braking systems use brake fluid to transfer the application of the brake pedal down to the front and rear brakes, to bring the vehicle to a stop.

The fluid is usually silicone based, which does not compress, giving a solid pedal feel and an increased temperature rating.

The downside to using this style of fluid, is that it absorbs moisture from the air.

Constant braking causes massive amounts of heat to be generated by the braking components, which is then transferred into the fluid.

If there is moisture in the fluid, this will decrease the temperature rating of the fluid, and can result in a soft brake pedal and increased stopping distance.

Regular brake fluid changes ensure that a car’s braking system operates safely and effectively.

Most manufacturers recommend brake fluid changes every 2 years, regardless of kilometres travelled, but it may need to be changed more frequently if the vehicle is operated under abnormal conditions. 

3. Clutch Fluid

Today’s manual transmission equipped vehicles use hydraulic clutch systems to transfer the application of the clutch pedal down to the gearbox and clutch assembly, allowing the driver to change gears smoothly and easily.

These systems use the same silicone based fluid that the braking system uses, so the same principals apply.

Most manufacturers recommend replacement of clutch fluid every 2 years, regardless of kilometres travelled, but this may need to be changed more frequently if the vehicle is operated under abnormal conditions. 

It’s industry standard to replace the brake and clutch fluid at the same time, to make sure both systems are operating correctly.

4. Engine Coolant

Engine coolant (Or Antifreeze) is designed to transfer the heat created by the combustion cycle, and disperse it through the cooling system of the engine.

This system includes the water pump - which pumps the coolant through passages in the engine, and the radiator - which transfers the heat from the fluid out into the atmosphere. It also provides the heat for the in car heater when switched on.

Coolant can come different colours, the main two being green - for cast iron engines, and red - for alloy based engines.

It’s important to use the correct colour coolant for the vehicle, as incorrect or mixing of the two can cause significant and expensive engine damage.

Normal life coolant is recommended to be changed every 3 to 5 years, depending on the vehicle and colour of the coolant.

Some manufacturers have started to make use of “Long-life” coolants, which can be Blue, Green or Red.

These types of coolant last much longer than standard coolant, and therefore do not to need to be replaced as often.

Long-life coolants can last up to 200,000km or 10 years, at which times the systems are flushed and coolant replaced.

If the vehicle is operated under abnormal conditions the cooling system and coolant may need to be serviced more often.

5. Transmission Fluid

Transmission fluid operates on the same basis as engine oil. It provides lubrication for moving parts, heat transfer and, in the case of automatic transmissions, enables the vehicle to move.

This fluid is designed to withstand enormous pressures and heat. Some transmissions incorporate a radiator, to allow heat transfer away from the moving parts inside the transmission.

In some cases, the fluid does not need to be changed for the life of the vehicle.

Most manufacturers include transmission servicing in certain logbook services, but it may need to be changed more frequently if the vehicle is operated under abnormal conditions (Have dropdown box of abnormal with list of conditions. 4wding, towing, racing, excessive stop-start driving).

In certain Volkswagen and Audi models fitted with a DSG or CVT automatic transmission, the transmission fluid is required to be changed every 60,000km, and failure to do so can cause significant and expensive transmission damage.

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Image credit: Pouring oil Robert Couse-Baker

Joel Ilton

Written By

Joel Ilton

Finding a passion for cars from a young age, Joel carried out work experience as a mechanic whilst at school before starting an apprenticeship after finishing year 12.

Joel is now the Workshop Manager at Robina Volkswagen.