SECTOR FOCUS: BASE OILS
The role of base oil quality in the production of finished lubricants
Nick Clague, Global Technical Manager, SK Lubricants
With the evolution of emissions legislation to ever tighter and tighter limits and also the need for improved fuel economy there have been significant changes in the requirements for engine oil lubricants over the past few years. The latest lubricants not only need to provide protection for the engine itself but they also need to be compatible with aftertreatment devices. Link all these requirements alongside the need for extended oil drain intervals and you can see why there has been such changes.
Lubricants are typically made up of additives (including viscosity modifiers and pour point depressants) and base oils. Base oils make up the majority of the formulation, typically 70-85% in engine oil but it can be much higher in industrial oils which have lower additive treat rates, and have several functions including heat dissipation and carrying additives to where they are needed in the engine.
There has been a big evolution in base oil technology in the last 20 years with the emergence of hydrocracked base oils over solvent refined base oils. These base oils offer improved low temperature properties with reduced volatility and have a higher saturates content. This, as well as reduced levels
of impurities had led to changes in formulation development and base oil selection is now a critical factor to be considered in any development.
The development of hydrocracked base oils, especially Group III base oils has been an enabler for the industry to move to 5W-30 (and lower viscosity grades) passenger car engine oils in Europe. European engine oils are typically used to lubricant both gasoline and diesel engines and have higher additive levels compared to ILSAC ‘GF’ or API ‘S’ oils as these specifications are only for gasoline engines. Additive packages are made up from several components some of which have poor low temperature properties. Therefore being able to blend these additives into Group III base oils allows the formulation to meet the low temperature and volatility performance requirements of the specification.
The other advantage of Group III base oils is that their quality is stable due to more consistent feedstock sources (typically fuels hydrocracker bottoms) and with these constant base oil qualities it allows the additive to be optimised in terms of not only treat rate but potentially the number of components in the additive package.
Figure 1: CCS and volatility comparison between Group II and Group III Continued on page 32 30 LUBE MAGAZINE NO.147 OCTOBER 2018
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