and here is the Shell tutorial page
If it was built prior to 2016, whether it is on- or off-highway, choose CK-4 oil which directly replaces CJ-4 oils
CK-4 oils will replace today’s lubricants and will be completely backwards compatible with all current engines. They will be designed with improved oxidation resistance, shear stability and aeration control.
Note, nothing is said about Friction Modifiers or "More Efficiency"
I found this down at the bottom of the page, surprise, surprise, look what Shell owns:
Shell Lubricants companies lead the lubricants industry, supplying more than 12% of global lubricants volume. * The companies manufacture and blend products for use in consumer, heavy industrial and commercial transport applications.
The Shell Lubricants portfolio of top-quality brands includes Pennzoil®, Quaker State®, FormulaShell®, Shell TELLUS®, Shell RIMULA®, Shell ROTELLA® T, Shell SPIRAX®, Shell Gadus® and Jiffy Lube®. *Kline & Company, “Global Lubricants Industry July 2015: Market Analysis and Assessment.”