Synthetic transmission oil for heavy-duty vehicles  

To meet the Paris Agreement’s climate goals, commercial vehicles need to reduce emissions by 80% by 2050. The European Union has set CO₂ reduction targets of 15% by 2025 and 30% by 2030 for commercial vehicles. To reach these goals, heavy-duty transmission fluids are moving toward lower viscosity – currently 10-14 cSt kinematic viscosity (KV) @ 100°C but trending lower – while striving to maintain, and even improve, wear protection and durability. 

Achieving these lubrication goals is especially difficult for heavy-duty vehicles, which must cope with higher shear, higher temperatures and higher wear compared to passenger vehicles. Increasing drain intervals from 300-500K KM to the target goal of 1M KM requires innovative formulations.

This chart shows the basic properties of three SAE 75W-90 gear oils – one made using SpectraSyn Elite™ 150, one using SpectraSyn Elite™ 65 and one using SpectraSyn™ 100. All the other components in the blends are the same. The Brookfield viscosity numbers at -40° C (ASTM D2893 test) show outstanding low-temperature performance capabilities.

Source ExxonMobil data

Source ExxonMobil data

Shear stability is taking on greater importance because of increased use of wide-span multigrade lubricants to improve fuel economy and service life. Because automotive gear lubricants typically contain viscosity modifiers that can shear in service, reducing viscosity and potentially leading to increased wear, stay-in-grade performance is part of the SAE J306 standard.

The three fully synthetic formulations in this chart do not contain polymers, but the high molecular weight PAO can suffer from shear. We can see that all three blends are very shear stable, remaining within the SAE 75W-90 spec even at extended test hours. These results demonstrate long lubricant life.

Extending drain intervals is increasingly important for commercial vehicles even as heavy-duty applications operate at higher temperatures. Base stocks that can provide improved oxidative stability help finished lubricants last longer and perform better in extreme conditions. In ExxonMobil tests, formulated oils using both SpectraSyn Elite mPAO and SpectraSyn PAO showed good performance. SpectraSyn Elite™ 65 and 150 provided superior performance.

Source ExxonMobil data