HOW IS OIL QUALITY MEASURED?
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.
FLASHPOINT
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
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.
