Main content | back to top
Myths about car oil
A lot of confusion about oil stems from popular myths which are mistaken for fact. Find out here whether what you ‘know’ is true or not.
Myths about engine oil
Myth 1: “If a small amount of oil is good, a lot is better.”
Overfilling the crankcase with oil is bad. It can cause excessive heat owing to the increased resistance, and thus shorten the oil’s life. In addition, a lot of oil will be splashed into the cylinders and cause excessive oil burning, increasing the combustion chamber deposits that can cause operational problems.
There is a popular belief that four litres of oil is just right for a four-cylinder car. This is not always the case. Check you car manual for the exact crankcase capacity as you may be able to save some oil for topping up. Remember to fill the crankcase to the level indicated on the dipstick – never more, never less.
Myth 2: “An engine oil that turns black is no good.”
On the contrary, an engine oil that does not turn black is a sign that the oil is not working. Modern engine oils contain detergent-dispersant additives that keep engine internal parts clean by removing carbon deposits and maintaining them in harmless suspension in the oil.
It is better to have the carbon deposits in the oil so they can be drained off than to have them left as deposits in the engine where they could do the most damage.
Myth 3: “All engine oils are the same.”
Engine oils differ in their physical characteristics, additive technology and additive content. Different oils are formulated to meet various specifications.
The selection of a suitable engine oil will depend on the engine manufacturer’s recommendation and the type of service the oil will be subjected to. Using the right type of oil can be more economical in the long run. To find the right oil for you, try our Shell LubeMatch tool here.
Myth 4: “Additives can boost engine oil and engine performance.”
Adding commercially available additives to engine oil is like adding sugar to your soft drink – you do not need it. Premium engine oils have been formulated with all the additives necessary to ensure optimum engine performance.
Additives cannot reduce oil consumption in an old engine or restore the engine protection properties of an old oil. In fact, additives may upset the oil chemistry and create new problems.
It is safer and more economical to use quality tested and ‘packaged’ premium oils. Do not waste your money on additives.
Myth 5: “Oil never wears out.”
Oil does wear out. The primary enemy of oil is heat. At high operating temperatures, oil begins to oxidise and thicken. Furthermore, engine oils can become laden with excessive carbon soot, water, acids, dust, metal particles and oxidised materials. These can cause plugging of oil filters and passageways or interfere with the proper action of some critical engine parts.
Change the oil regularly at the recommended oil-change interval.