Car engine

Engine oil is an essential fluid that keeps an engine running. It is a mixture of mineral oil or synthetic compounds and additives such as antioxidants, detergents and stabilizers. Some may ask, what does oil do in a car engine? The main functions of engine oil are to lubricate moving engine parts, clean them, cool components and protect the metal from wearing out.

Modern synthetic oils are extremely efficient at working in temperatures that are close to freezing and also at high temperatures. They remain viscous and offer superior lubricating properties, and cooling and cleaning functions.

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Why is oil needed?

Engine oil is more than just a lubricants. It also cools, cleans and protects sensitive engine components and prevents damage at extreme temperatures. Engine oil can also improve the performance of an engine by letting it rev freely without overheating.

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So, what does engine oil do for your car? Some of the important functions of engine oil in a car include the following:

  • Lubrication of moving parts to reduce friction between them
  • Reducing engine component wear and tear
  • Cleaning carbon deposits from the combustion process
  • Carrying away dirt and debris, and suspended contaminants by either dissolving them or passing them through an oil filter
  • Reducing the harmful emissions by allowing a clean combustion process at a controlled temperature
  • Cooling engine parts using an oil cooler/radiator
  • Providing the necessary hydraulic pressure in valvetrains
  • Protecting the delicate metal parts of the piston and cylinder
  • Improving fuel economy
  • Remaining viscous and providing lubrication at extreme temperatures

This list answers the question, why is oil needed? It is impossible for a car engine to run without engine oil. It would simply overheat and the components would break down soon after driving.

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What does engine oil consist of?

Engine oil comes in different types, but the most common are mineral oils and synthetic oils. The base oil comes from crude oil (known as lubrication fuel oils), mixed with additives that enhance the function and properties of engine oil.

The additive contains chemicals such as:

Detergents – get rid of dirt, sludge, carbon deposits and contaminants

Antioxidants – to prevent the oil from degrading due to exposure

Dispersants – to help distribute the oil freely in the engine

Anti-wear additives – reduce the wear and tear of metal components

Friction additives – to allow the parts to move smoothly against each other

Corrosion inhibitors – these additives inhibit corrosion and rust forming on metal components

Anti-foam additives – keep the oil stable and prevents foaming

Viscosity improvers – keep the oil from getting too thick in cold temperatures and too thin in high temperatures

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How does engine oil provide cleaning?

As fuel burns, there are several contaminants, reside and carbon deposits that get left behind and find their way into the engine oil. Over time this residue builds up as sludge and causes the oil to become thicker while losing its lubricating properties. You often see this as dark-coloured oil which is replaced from an engine with high mileage.

Sludge is often formed in low-quality engine oil or oil that has been circulating in an engine for a long time. The result is poor lubrication, overheating and poor performance from the engine. In this case, the old oil should be removed and an engine flush should be added. An engine flush contains detergents that dissolve the dirt that has been stuck in the oil galleries and valve trains as well as the piston rings and combustion chamber.

Once the internals has been cleaned; you should pour in the right amount of oil which should last at least 5,000 km in an internal combustion petrol engine. Diesel engines require more frequent oil changes because of the heavy fuel and incomplete combustion process.

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Is oil on engine bad?

When filling new oil in an engine it is common for the exterior components to get splashed with oil, especially when you unscrew the drain plug and later fill in the oil through the top of the cylinder head. 

Wipe away spilt oil with a solvent and cloth to keep your engine bay looking clean. You don’t want the oil to burn and smoke away while driving or damage the delicate plastic finish of the engine cover.

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Engine oil flows through the internal components lubricating moving parts. The 5 main functions of oil include reducing friction, preventing heat build-up, cleaning, maintain optimum performance, controlling rust and corrosion, maintaining viscosity and decreasing oxidation effects.

Due to these properties, engine oil ensures a long life for the engine, provides proper running of the engine while reducing sounds of moving parts, improves fuel economy and reduces carbon dioxide emissions.

The different types of engine oil available for vehicles include mineral oil, semi-synthetic and fully synthetic. Mineral oils are derived from crude oil fractional distillation while synthetic oils are made in a lab, specifically designed to be used in vehicle engines.

They also come in different grades to signify that they retain their viscosity in cold or hot temperatures. To choose the best oil for your vehicle, refer to your owner’s manual or visit your designated service centre where a technician can advise you on the perfect oil to suit your car.

This article should help you learn about engine oils and their function. Other interesting articles on our blog including Why do car engines overheat and how to deal with them? and How to Check Engine Oil Level or visit Carorbis Blog for more.

Frequently Asked Questions

Q1. How much oil does an engine need?

Ans. Every engine is built with different specifications that require varying amounts of oil. If you refer to the owner’s manual, you will find the exact quantity of oil to refill into your engine, including the type, grade and even the brand that is most suitable. Some large engine will need more than 1 litre of oil whereas small capacity engine requires much less, around 750 ml. In contrast, a motorcycle engine may need only ½ a litre of engine oil. The oil dipstick indicates the correct level to which oil must be refilled in an engine.

Q2. How long does oil last in engine?

Ans. The type of engine oil used in an internal combustion powerplant determines how long it will last. Typically, engine oil is replaced every 5000 km or 3 months, whichever is sooner. Some types of synthetic oil can run in an engine for considerably longer, up to 7000 km or 5 months. Engine oil deteriorates over time and sludge, carbon deposits and metal shaving accumulate as the engine is run. It is best to change the engine oil if you notice overheating, sluggish performance or a burning smell when you accelerate or drive at high speeds.

Q3. What happens if I run my engine without oil?

Ans. One of the main functions of engine oil is to provide lubrication between moving parts to reduce friction and prevent heat from building up, eventually damaging internal engine components. Engine oil also carries away carbon deposits, sludge and metal shaving away from moving parts and passes it through a filter to keep it from being circulated within the engine. If you run an engine without oil, it would soon overheat and lock up, the pistons fusing with cylinders and valvetrains and transmissions breaking apart due to friction. You would be looking at a complete engine replacement at this point.

Q4. How does oil get into the engine?

Ans. The oil is filled through the oil filler cap above the engine head and accumulates at the bottom of the engine block in the oil sump. The oil sump consists of a reservoir and oil pump that forces engine oil through an oil filter to the main bearings of the crankshaft, valve train, pistons, cylinders and other moving components. The engine oil moves through oil holes drilled in various parts through oil galleries and ends up back in the oil sump reservoir where the oil pump recirculates it through the engine.

Q5. What happens if engine has no oil?

Ans. Engine oil is used to reduce friction between moving parts, for cooling of pistons, and cylinders where internal combustion takes place and for cleaning the carbon deposits and sludge by-products from burning fuel and moving metal components. Without engine oil, the engine would overheat very quickly and destroy itself. Engine temperatures reach in excess of 100 degrees Celsius and will melt metal parts after a short while of driving. Basically, the engine cannot function without engine oil.

Q6. What does oil do for a car engine?

Ans. Engine oil is mainly used for lubrication in order to reduce friction between the piston and cylinder, and other moving parts. Essentially, the oil smoothens the movement and prevents heat build-up by creating a thin film between two metal parts. Engine oil is also used to carry away the heat from the combustion process and dissipate high temperatures in an oil cooler. There are also impurities from the combustion process, by-products of heated oil (sludge, dirt and metal debris from moving parts), and carbon deposits. Engine oil cleans these impurities and filters them out before recirculating through the engine.

Q7. What happens if I get oil on my engine?

Ans. Oil is not flammable and is able to absorb heat without vaporising or catching fire. However, if you do spill oil on the exhaust manifold which reaches very high temperatures, there is a chance of fire due to igniting oil. External engine parts usually do not get damaged from spilt oil; however, it is a good idea to clean oil spills with a solvent and cloth to prevent sticky residue from building up which may attract dust and debris. Plus, the oil may burn and smoke creating an obnoxious odour in the engine bay that may creep into the cabin.

Q8. Is it normal to have oil on engine?

Ans. During an oil change procedure, it is very likely that you will spill a small amount of oil onto the engine. In order to get engine oil out of the block, a drain plug will have to be undone from below the vehicle. This will invariably splash oil onto various engine parts. When filling the oil, if you don’t use a funnel, there is a chance oil may spill onto the engine cover and other parts. Although this is expected, it is always a good idea to clean oil spills with a solvent and microfibre cloth to prevent any fire hazards or nasty results of burning oil.

Q9. What happens to the engine when oil is low?

Ans. When there is a low level of engine oil, internal engine components will receive inadequate oil and those parts cannot be lubricated properly. Symptoms of low engine oil include grinding sounds, overheating, the smell of burning oil, high fuel consumption and sluggish performance when accelerating. The engine oil pump may also begin to malfunction due to low oil pressure.

Q10. What are the main 3 functions of engine oil?

Ans. Engine oil is responsible for lubrication, cooling and cleaning. Lubrication is a property of an oil that reduces friction and heat between moving engine parts. Cooling occurs when engine oil absorbs heat from the engine block and dissipates it in the oil cooler. The engine oil also cleans carbon deposits, sludge, burnt particles and dirt through the use of detergents and other oil additives.

Q11. How does oil make a car run?

Ans. The engine consists of complicated mechanical components that have to work in tandem in order to produce power. Engine oil is used as a lubricant to keep these parts moving smoothly, reduce friction and to prevent metal parts from wearing out by rubbing against each other. The oil pump draws oil from the sump under pressure and sends it to the crankshaft main bearings and cylinder head. The oil makes its way through the valve train lubricating all the moving parts and cooling them in the process.

Q12. How often should engine oil be changed?

Ans. Most cars need an oil change every 5,000 km or 3 months. Synthetic oils last longer in the engine and retain their lubricating properties for up to 7,000 km. Since oil deteriorates over time due to heat and oxidation, it must be changed in order to function properly. Oil can also lose its viscosity when exposed to moisture from the atmosphere. 

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