From coolants to the types of oils, our Car Doctor can help.
Fluids
Can coolants be mixed?
You should stick to the recommendations outlined in your vehicle owner’s handbook. This is particularly true with regards to modern vehicles, whose cooling systems require specific types and concentrations of engine coolants. Mixing coolants can alter both of these. When your car is serviced, the technician will inspect your cooling system including the coolant and if necessary they can test to see if it is still within required specifications. If the coolant does not pass the test they will recommend a flush and replacement of the coolant.
Can you top up low levels of coolant with water in an emergency?
Normal tap water contains many contaminants that can cause damage to your vehicle’s cooling system. You should only use distilled water to top up the system. If normal tap water is put into the cooling system you will need to have the system flushed out and the coolant replaced as soon as possible.
What does it mean when my mechanic says the brake fluid is "contaminated"?
Most manufacturers recommend changing the brake fluid every two years irrespective of the kilometres travelled, due to brake‑fluid deterioration and contamination, which can cause brake failure. Brake‑fluid contamination can be caused by something as simple as dipping an oily finger in the brake fluid. Brake fluid is also hydroscopic (meaning it absorbs moisture), this can lower the fluid’s boiling point and cause brake system components to corrode internally, causing premature failure. Heat generated from the brakes can cause the water‑logged fluid to boil, which can cause sudden or unexpected brake failure. Brake fluid should be changed as recommended for your safety and that of other road users.
How do I know when my car coolant needs to be changed?
It is normal practice for the interval to be every 24 to 48 months, however your vehicle’s service manual will show the recommended coolant changing interval. It is important that you use coolant that adheres to the specifications recommended by the manufacturer. In most cases you will be able to use coolant that has the same specifications as the manufacturer-branded coolant, but is generically labelled. In any case, it is also important not to mix two different types of coolant.
What’s the difference between synthetic oil and normal oil?
Synthetic oil is generally preferable to mineral oils for modern vehicles. It operates better at lower temperatures because the lower viscosity of synthetic oil means it is able to flow and lubricate the engine at cold starts more easily. Furthermore, at high operating temperatures, the molecules in synthetic oil do not break down as easily, thus protecting the engine from excessive wear over time. However, manufacturers specify the most appropriate oil to use in their vehicles to ensure consumers get the best out of the vehicle. Using different oil from the manufacturer’s specification can be detrimental to the vehicle’s fuel consumption and/or its engine’s life.
Does oil quality drop if it is stored in a sealed container?
It is best practice to use vehicle fluids that are as fresh as possible. There is an expiry date on the containers and it is best to adhere to this. Keep the bottle(s) in an area that is as cool as possible and not exposed to any elements.
Is it still necessary to change oil four times annually if I drive less than 10,000km per year?
Changing the oil at regular intervals will help prolong the life of the engine. Oil does degrade over a period of time. However, to get the best performance out of your engine without any unnecessary extra outlay on maintenance, we recommend changing the oil in line with the manufacturer’s recommendations, which in the case of your vehicle is every 12 months or 15,000km, whichever comes first.
What happens if you over fill your engine with too much oil?
The amount of damage done to an engine as a result of being over-filled with oil will depend on the amount by which it was over-filled.
If excessively overfilled, extensive damage can be done. If the level is too high the piston can splash into the oil causing several problems:
- Aeration of the oil and loss of oil pressure
- Excessive crankshaft pressure, which can cause the oil to be forced out of the engine dipstick hole, oil filler or crankcase ventilation valve
- Excessive oil burning
- Hydraulic lock of the engine causing damage to major components
If you have overfilled your engine, your mechanic or RAC Auto Services will be able to help.
