Havoline Oils – Part One

Lubricants are an essential part of any engine’s wellbeing, but do we really understand or appreciate the technology and terminology behind the products? Texaco Product & Technology Support Chemist, Rudi Sanders takes us back to basics.

What do the letters and numbers in motor oil classification mean?

The Society of Automotive Engineers was originally responsible for developing a system to classify engine oils, this was known as the SAE Engine Oil Viscosity Classification J300. 

SAE J300 contains two sub-classifications, a “W” grade, relating to the low temperature flow properties of an engine oil and a “non-W” grade designation, relating to viscosity operating temperature properties. W-grade and non-W grade oils are sometimes referred to respectively as the ‘Winter’ grade and the ‘Summer’ grade, hence the “W” we commonly see in oil classifications.  

The numbers before and after the “W” relate to the viscosity of the oil. The number before “W”, represents the oil viscosity at low temperatures and the number after the “W”, how thick the oil is during the engine’s normal operating temperature.

If we deep dive into how the oils are classified, there are a number of technical components to the classification status. Low temperature viscosity requirements are defined by both a cranking viscosity and pumping viscosity measurement. The cranking viscosity is measured by the Cold Cranking Simulator (CCS) test to evaluate the cranking resistance of an engine oil. If the CCS viscosity limit for a specified oil is exceeded, the battery and starter motor may not be able to crank the engine at a sufficient speed to allow the engine to start.

The pumping viscosity is measured by the Mini-Rotary Viscometer (MRV) test. This test also determines the presence of yield stress, assessing the ability of an oil to flow through the oil pick-up tube. If the pumping viscosity, or yield stress of an engine oil are too high, an engine can be starved of oil during the first few minutes of operation. The temperature for the pumping viscosity measurement is 5°C below the cranking viscosity measurement temperature to ensure that oils which help with engine start-up will also pump adequately.

The operating temperature viscosity requirements are defined by kinematic viscosity measurements at 100°C and by high shear rate viscosity measurements at 150°C. There are minimum kinematic viscosity limits for each W-grade, but no maximum, whereas non-W grades have minimum and maximum limits. The high shear viscosity is measured at 150°C and at a shear rate of 106s-1. These are typical conditions in engine bearings during operation.

Oils which meet the requirement of only one sub-classification are referred to as single or mono-grade oils for example SAE 10W or SAE 30. oils, that are labelled as meeting the requirements of both a W and a non-W designated grade, which are called multigrade oils such as 10W-30.

What does the term lower viscosity mean as it relates to oil?

Lower viscosity is a relative term that changes over time. Previously, oils which seem standard today, such as SAE 10W-30 or SAE 5W-30 were described as low viscosity oils when compared to the typical SAE 20W-50, 15W-40 & 10W-40 viscosity oils at that time.

Today, we speak about lower viscosity oil if we have engine oils for which the “W” grade is 5 or 0 and the non-W grade is 20 and lower. Currently, low viscosity relates to multigrade engine oils with a high shear rate viscosity at 150°C of less than 2.9 cP.

It is important to remember that engine oils with a high shear rate viscosity at 150°C of less than 2.9 cP cannot be used in many older engines, as they will lead to excessive engine wear and eventually engine seizure. Today, several engine manufacturers are developing engines than can cope with engine oils with high shear at 150°C of 2.3 cP and lower.

What are additives and why are they so important?

To function effectively engine oil requires chemical components called additives. Additives help protect the engine and improve and maintain the performance of the engine oils. Without the addition of high performing additives to the base fluids, oils would not survive the conditions created in a modern engine. 

An engine oil consists of a base fluid with a combination of different additives in complex and carefully balanced formulas. Depending on the specific application, various combinations of additives are used to meet the required performance level.  Each additive has an important role to play in protecting and optimising the engine, some of the most important of which we can see in the list below.

Further information on the full range of Texaco Havoline products can be found here.

Original: By Chevron Technology