on their read across rules, and an official “plus” categorisation has not been defined. Therefore, this categorisation, such as that of a Group II+ vs a Group II, is a marketing decision based on the anecdotal meaning of the pluses relative to the improvement of performance of the base stocks. There are several properties to consider when labelling a base stock as a “plus.”
“Plus” properties and benefits While the industry has not officially defined “plus” base stocks, there are several properties of base stocks that factor into whether marketers label it a “plus” – primarily Cold Cranking Simulator (CCS) performance, NOACK volatility and viscosity index (VI) for Group II+ and III+.
Focusing on Group II+ base stocks, there is improved CCS and NOACK volatility versus Group II base stocks at the same viscosity so the base stock can be used in more advanced lubricant formulations and applications. However, the label of “plus” is related to how the base stock can be used and not just those specific properties. Meaning there is not a particular CCS, VI, or NOACK which defines a “plus” base stock, but rather it’s the combination of the three that allows the base stock to be used more advantageously. Group II+ enables manufacturers to reduce or eliminate the need for Group III from certain formulations and provides advantages for certain applications versus conventional Group II. Some primary differences between Group II+ and Group III and VI are price.
Finished lubricant manufacturers recognise the importance of minimising production costs while maximising performance of their products. In many instances a Group III base stock used to blend an SAE 5W-30 engine oil, for example, could be easily replaced by a high-quality Group II+ with a lower price point. Simply put, Group II+ can be considered the base stock sweet spot – delivering the performance needed for a typically lower price.
Using a Group II+ also has the potential to provide reduced manufacturing complexity. Instead of having a tank filled with Group II and another tank filled with Group III, manufacturers may only need one tank filled with Group II+ to blend lubricants. This potential efficiency could translate into cost savings for the lubricant producer.
The performance benefits of Group II+ vs Group II base stocks are specifically seen on the finished lubricant side and making the move to Group II+ is a decision dependent upon the mix of products the manufacturer makes. In certain industrial lubricants, some of the performance characteristics of Group II+ may not be valued. In those cases, Group II+ may not be the preferred base stock for the application. If the target application is automotive then the formulation benefits of high-quality Group II+ base stock may make it the optimal choice.
Not all “Plus” is created equal When it comes to engine oil, there is a big shift from conventional (i.e. mineral based) oil to semi-synthetic and synthetics to provide better engine performance and protection.
The heart of these advanced lubricants is the lower volatility and better oxidation performance, meaning it doesn’t thicken as quickly as a mineral oil and won’t evaporate or degrade as quickly either. This leads to better wear protection, reduces sludge build up, keeps engines cleaner, and allows the oil to perform better at high and low temperatures. All of these factors ultimately enable users to extend their oil drain intervals (ODI) which is a driving force behind this shift to semi-synthetic and synthetic lubricants.
Group II+ base stocks can be used in semi-synthetic and synthetic lubricants, but the use depends on the scenario. Not all Group II+ base stocks are created equal and minor differences can play a big part in finished lubricant performance. The use of Group II+ base stocks in semi-synthetic and synthetic lubricants is often a marketing decision based on performance. Notably, a lot of the same molecules in Group II+ are in Group III, and Group II+ can also meet the threshold of performance capabilities for Group III base stocks. This makes Group II+ comparable to a Group III for many formulations.
Ultimately, as “plus” base stocks production increases, it’s important that lubrication manufacturers continue to focus on the necessary properties of their products and use base stocks that enable the best performance at the best value.
LINK
www.exxonmobil.com/basestocks
LUBE MAGAZINE NO.161 FEBRUARY 2021
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