The drive to improve fuel economy among engine manufacturers has been taking place for some time and to do this, the industry has been moving towards lower viscosity solutions, demonstrated by launch of API CK-4 and FA-4 oil categories in December 2016.
- API FA-4 specifies an HTHS viscosity between 2.9 and 3.2 cP
- API CK-4 specifies an HTHS equal to or greater than 3.5 cP
API FA-4 oils with lower HTHS offer potential increased fuel efficiency, but are be restricted to newer engines designed to run on these lower HTHS viscosity oils. This does exclude some older engines found in existing fleets as the oil was not designed for the older engine hardware.
Lower viscosity API FA-4 oils minimize frictional losses between moving components of the engine and reduce pumping and rotational losses, resulting in less viscous drag and improved fuel economy. This enables engines to run more efficiently and use less fuel, while still offering improved levels of wear protection by delivering oil more efficiently to moving parts within the engine.
Adopting Low HTHS Viscosity Oils
Engine manufacturers may have begun to adapt their engine design to FA-4 requirements and enable end users to achieve the greater fuel economy provided by low HTHS viscosity oils.
API CK-4 oils with a HTHS viscosity equal to or greater than 3.5 would cover the heritage fleet, plus any new engines requiring higher HTHS viscosity for wear protection (typically off-highway usage).
Between April 2013 and January 2015, the SAE incorporated three new viscosity grades to their J300 viscosity grade and classification standard for motor oils (see SAE J300 Table of Viscosity Grades for Engine Oils).
In pursuit of the higher fuel economy, they offer:
- SAE 16 – 2.3 mPa·s
- SAE 12 – 2.0 mPa·s
- SAE 8 – 1.7 mPa·s
These viscosity grades with significantly lower HTHS are only applicable to passenger car hardware at present.
The demand of higher fuel economy is only going to continue and as such, lubricant manufacturers are continually striving for lower HTHS viscosity oils. At Petro-Canada Lubricants, we’re asking ‘how low can we go?’ and testing oils at an HTHS viscosity below 2.9 cP. It’s still important to consider the balance between protection and ease and movement, but if we can demonstrate that a 0W-20 oil can protect as well as a 10W-30 or a 15W-40 and still provide the fuel economy benefits, it could be a real step forward in the future of engine oils.