AMSOIL recently put their AMSOIL Premium API CJ-4 5W-40 Synthetic Diesel Oil (DEO) up against four competing 5W-40’s in shear stability testing which was performed by an independent laboratory. AMSOIL put “DEO” up against Mobil Delvac 1 ESP, Shell Rotella T, Chevron Delo 400T and Valvoline Premium Blue Extreme in the Kurt Orbahn (ASTM D-6278) Shear Stability Test as shown in the article AMSOIL CJ-4 5W-40 Outperforms in Shear Stability Test.
As the article explains, 2007 and newer diesel engines offer a multitude of challenges to motor oil and fuel dilution is (by far) the biggest. To show the mettle of AMSOIL DEO 5W-40, the shear test was doubled from the industry standard of 90 cycles to 180 cycles. Then the test was performed with 2% fuel dilution and then 4% fuel dilution.