Unlike passenger car engine oils, heavy-duty engine oils have been slow to migrate to lower viscosity grades. The pace is slower, but the trend is clear: Lower-viscosity HDEO continues to displace demand for SAE 15W-40, primarily in favor of 10W-30. This shift from heavier to lighter viscosity will continue as OEMs drive toward higher fuel efficiency and lower emissions.
The evolution of HDEO viscosity grades started with the declining use of monogrades following the introduction of multigrades in the 1950s. While it took nearly 30 years for the transition to reach an inflection point, demand for monogrades was supplanted primarily by SAE 15W-40, dropping to roughly 30% in the 1990s. Today, monogrades account for less than 3% of demand in North America and continue to decline globally.
Even though SAE 15W-40 was the dominant viscosity grade for over 30 years, it too is being transitioned out of the market in favor of more fuel-efficient SAE 10W-30 and lighter grades. From its peak at over 80% of market share in 2010, 15W-40 demand fell to about 67% in 2022, according to Infineum.