A side-on view of an engine

Synthetic base stocks for low-viscosity engine oils

Engine and lubricant technologies for passenger and commercial vehicles continue to evolve, driven mainly by the need to improve fuel economy and reduce emissions. Base stocks with lower viscosity and volatility characteristics can help meet these challenges, but the lower the viscosity, the higher the volatility. Formulators also struggle to create engine oils that deliver fuel economy at lower viscosity without compromising wear protection.

Our low-viscosity SpectraSyn™ polyalphaolefin (PAO) synthetic base stocks, available between 2 and 10 cSt @ 100°C, offer numerous advantages over mineral-oil base stocks, including:

  • Excellent low-temperature properties for improved low-temperature performance
  • Low volatility (Noack) for reduced oil consumption
  • Better oxidative and thermal stability for engine cleanliness and longer drain intervals
  • Improved lubricity for fuel economy improvements

Formulators blend low-viscosity SpectraSyn PAO with mineral base stocks to provide these performance enhancements in finished engine oils.

Low volatility

Despite their low viscosity, SpectraSyn PAO base stocks provide low volatility at high temperatures compared to mineral-based fluid. This capability helps lower oil consumption, a key benefit for today’s smaller sump sizes, while minimizing emissions and extending drain intervals. In Noack volatility testing, our PAO base stocks demonstrate lower volatility than Group I, II and III mineral oils.

Available in viscosity ranges between 2 and 10 cSt kinematic viscosity at 100°C, SpectraSyn™ PAOs offer a cost-effective way to enhance mineral base stock blends and boost finished engine oil performance.  

Noack/viscocity curve for group 1, 2, and 3 base stocks.

Low-temperature performance

The CCS test measures the apparent viscosity of fluids at low temperatures (typically between -10 to -35°C), and high shear rates ( 10-6 sec-1). It measures the ease of engine cold crank starting. Lower viscosities at low temperature also allow the oil to flow and lubricate the engine parts, reducing strain and increasing protection. The graph shows that even at similar viscosity (KV 100) and VI, PAOs have significantly lower viscosity at low temperatures compared to a Group III mineral oil. These differences are also evident at CCS tests performed at -30 and -35°C.

Thermal-oxidative stability

Synthetic base stocks have excellent thermal-oxidative stability, which helps minimize deposit formation in the engine – thereby enhancing cleanliness and durability. Group V synthetic base stocks such as alkylated naphthalene and esters have very high thermal-oxidative stability and excellent solubility, enabling them to dissolve oxidation products and prevent deposits and sludge formation. By protecting engines from deposits and sludge, these synthetic base stocks can improve engine life, which can provide sustainability benefits through reduced use of materials and other resources.

The chart shows that low-viscosity SpectraSyn™ PAO maintains viscosity longer than three Group III base oils during aging tests.

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