Understanding Engine Oil

Motor Oil lubrication is essential for cooling vital engine components, reducing friction and preventing wear by forming a thin oil film on crankshaft bearing surfaces that separates moving parts so they don’t come into direct contact. The oil film behaves like a shock absorber that cushions moving and rotating parts inside the engine. Motor oil reduces rust and corrosion inside the engine as well as helps keep surfaces clean by dissolving and carrying dirt deposits to the oil filter

Understanding Viscosity

Viscosity is defined as the oil's resistance to flow or the speed of its flow. The thicker the oil the slower it will flow (higher viscosity). Thinner oils (lower Viscosity) have a water-like consistency and pour more easily at low temperatures, while heavier thicker oils have more of a honey-like consistency.

Additives can alter the way oil behaves at low and high temperatures and multi-grade oils have a wide viscosity range across different temperatures. Take 5W30 for instance;

‘W’ stands for winter which is why the first number of the grade followed by the ‘W’ describes the viscosity of the oil at a low temperature. While the second number (in this case 30) describes the thickness of the oil at engine running temperature (around 100°C)

Multi-grade oils are designed to flow well at low temperatures and be able to adequately lubricate the engine at a cold start while also maintaining thickness and lubricant film strength at hot temperature. If the oil is too thin at the hot temperature it may not protect the engine effectively or if its too thick, the engine may not run efficiently. The correct viscosity grade will be indicated on your vehicle service manual.

The importance of regular oil servicing

Regardless of mineral or synthetic, viscosity grade or brand, all motor oil will eventually wear out and needs to be changed at regular service intervals for an engine to maintain optimum performance. As the miles start adding up the oil starts to wear and get dirty from worn oil additives. As a result, the oil will no longer have the same lubrication ability or the viscosity range it first had when it was new.

When an oil service is due to the current oil will by now contain a mixture of acids, soot, moisture and metal particles from normal wear. At this point, fuel consumption & emissions may increase and engine power may decline. It is, therefore, crucial to follow scheduled service intervals in order to maintain efficient engine performance.


Choosing the right oil

What you need to know about ottolube oil?

Many vehicle manufacturers recommend using 5W30 motor oil for year-round driving. Other manufacturers specify 10W40 or 0W20. It is best to always refer to your service manual for correct viscosity recommendation. Sometimes the viscosity recommended for your car is indicated on the oil filler cap or dipstick. However, As the mileage of any car adds up there will be increased wear of internal engine bearing clearances, in this case it may be applicable to switch to a slightly higher viscosity grade to prolong engine life, reduce fuel consumption and noise; for example, if a vehicle manufacturer usually recommends 5W30 for a car that now has 100,000 miles it may be wise to either use 10W30 or 10W40 to provide better lubrication and protection.

We can also help you choose the correct oil viscosity by entering your car registration number into our oil recommender.

Oil pump

The force that drives motor oil inside the engine is the oil pump. The spur gears inside the pump drive oil from the oil sump and push it through the oil passages which direct it to where its needed inside the engine. The oil is pumped through the engine block to the connecting rods, bearings, pistons and the crankshaft allowing it to keep rotating with minimal friction. The oil pump also pushes oil to the camshafts which provide friction reduction and protection from wear to some of the heaviest loaded parts inside an engine. The constant oil flow also provides much-needed cooling.

Oil Filter

Motor oil lubricates, cools and helps keep surfaces inside the engine clean by carrying dirt deposits to the oil filter. The oil filter is one of the engine's main defences against dirt and solid contaminants such as carbon and metal particles. It is the only defence against abrasion and the premature wear it causes. The oil filter removes these contaminants from the oil before they can damage bearings and cylinder wall surfaces inside the engine. It is therefore always wise to invest in a high-quality oil filter with every oil service.

Many Modern day engines installed a system called “full flow filtration” that collects the oil through the oil pump and lead it straight to the oil filter before it gets to the crankshaft, bearings and camshafts. This method ensures clean filtered oil is circulated around the engine from the start. Over time the accumulated dirt and debris trapped by the oil filter can cause obstruction to normal oil flow. It is crucial that the oil filter is changed before it reaches this point otherwise the pressure will force the bypass valve to open which will allow unfiltered oil to circulate the engine.

Most professional technicians will recommend oil filter replacement with every oil change even though some service manuals will state that it is acceptable to replace oil filters every other oil change. But why contaminate new oil with a used oil filter? A new oil filter is a cheap insurance against premature wear that could risk costly damage to an engine if the old oil filter is on the verge of clogging up.

How to compare oil specifications to determine oil characteristics and performance?

When comparing two or more oils for possible use in your vehicle, the important thing to do is to compare technical specifications of each oil.

Below we have listed not all, but some of the most important technical specifications needed to compare oils.

  1. Viscosity Index (VI)
  2. Cold Crank Simulator Viscosity (CCS)
  3. Pour Point
  4. Flash Point
  5. Total Base Number (TBN)
  6. Sulphated Ash Content

Viscosity Index (VI)

An oil's VI refers to the oils ability to maintain a consistent viscosity across a wide temperature range. The higher the value the better this ability. In our opinion, a decent multi-viscosity oil should have a VI above 150.

Cold Crank Simulator Viscosity (CCS)

The CCS measures the “stability” of an oil by simulating the conditions of a rotating crankshaft when the oil is cooled to a certain temperature. For any oil to claim a viscosity grade it must pass a CCS test at the specified temperature. For example, 5w30 must pass CCS test at a temperature of -30 °C with a score described in the SAE J300 requirements for engine oil specification. When comparing CCS values be careful not to assume that the score is a measurement of the shaft rotation speed. If it was, a high number would be better. This is not the case. It’s a measure of pressure and viscosity and you want a low value on the CCS test. The lower the value the thinner the oil at low temperature.

Pour point

The pour point is the lowest temperature that oil will actually flow. This doesn’t mean that the oil will circulate the engine adequately at this temperature. It is just an indication that the oil will still somewhat behave like a liquid at this temperature.


This is the temperature at which the oil vaporises enough for the gas to become momentarily flammable in the presence of a small flame. In today's modern day engines, we believe that a flash point below 200°C is unacceptable. A good quality synthetic oil should be above this.


TBN is an oils indication of how well it can neutralise acid build up within an oil and for how long it can do it. The higher the value the better equipped the oil is to neutralise acids from condensation, oxidation and combustion by-products.

Sulphated ash

The sulphated ash content of an oil is important because it can indicate how much deposit build up an oil will leave in your engine. It is particularly important to consider the value if your vehicle has DPF or catalytic converter installed.