Will SAE 16 synthetic motor oil replace SAE 20 in future car engines?

SAE 16 synthetic motor oil, formally labeled as SAE 16 in April of 2013 by the Society of Automotive Engineers (SAE) was introduced as a new, low viscosity grade specification to help OEMs meet increasingly strict corporate average fuel economy (CAFE) requirements.

However, ultra-low viscosity grade oils can create durability challenges that need to be carefully considered.

  

Image credit: Duke Engines

SAE 16 synthetic motor oil is a lighter-weight alternative to SAE 20.

SAE 16 synthetic motor oil will serve as a lighter-weight alternative to SAE 20. With kinematic viscosity (KV) limits set at 6.1 – 8.2 mm2/s at 100°C, the main objective behind SAE 16 synthetic motor oil is to better facilitate fuel efficiency in engines by reducing hydrodynamic friction between moving parts, such as piston rings, bearings and valve trains.

Strict SAE 16 synthetic motor oil specifications to combat emissions.

To improve fuel economy and reduce emissions, a reduction in the engine lubricant’s high-temperature, high-shear (HTHS) viscosity limits have also been specified in the SAE 16 synthetic engine oil spec sheet. For the first time ever the SAE has defined this limit below 2.6 - setting the minimum to 2.3 mPa⋅s at 150°C.

While SAE 16 synthetic motor oil will help improve fuel efficiency throughout the entire service life of the oil, it could increase wear and tear on critical engine parts. To combat this a new generation of additives suitable for ultra-thin oils in high power density engines has to be developed.

In addition to the introduction of SAE 16 viscosity grade for SAE 16 synthetic motor oil last April, the new revision to J300 Viscosity Grade also included a change in the minimum high-temperature viscosity range of SAE 20. With a previously set KV minimum limit measured at 100°C of 5.6 mm2/s, the lower portion of the SAE 20 engine oil range was not being utilized by OEMs. As a result, the limit was raised to 6.9 mm2/s, which effectively narrowed SAE 20’s range and made it similar to that of higher-viscosity grades.

 The revisions made to the J300 Classification Standard have paved the way for low viscosity SAE XW-16 motor oils. This will have a significant impact on the GF-6 engine oil performance category, especially because of its proposed split into two separate subcategories: GF-6A and GF-6B.

While GF-6A oils (i.e., SAE 0W-20 motor oil) will incorporate all the measures of protection required for use in gasoline direct injection (GDI) engines, along with other innovative automotive technologies that haven’t yet reached the market, it will be rearwards compatible with all applications currently approved for GF-5.

As a result, the viscosity of SAE 16 synthetic motor oil will be low but not so low that it can’t protect against wear and corrosion in older engines.

GF-6B, on the other hand, forgoes the requirement to be backwards compatible with GF-5 applications and opens the door for the development of ultra-low viscosity lubricants (i.e., SAE 16 synthetic motor oil) that will push the industry into areas of formulation that have never before been encountered. These lubricants will produce significant fuel economy benefits for many engine applications, but because of their low viscosity grade, there is the potential for wear or other durability related issues.

While it is generally accepted that lower viscosity brings an improvement in fuel economy performance and potentially lower emissions, it can have a negative impact on durability because the protective oil film is less robust, or under the most extreme loading conditions, non-existent. In terms of performance requirements, this translates to a set of standards that will ensure fuel economy is improved via lower viscosity, but durability will not be compromised.

The future of SAE 16 synthetic motor oil.

The future proposed ultra-low viscosity GF-6B specification requires the same durability performance as the proposed GF-6A. This may require enhanced fortification of specific additive components or a different formulation shape to deliver the required durability in SAE XW-16 lubricants.

Pushing the limits of engine oil formulation with SAE 16 synthetic motor oil will require a new generation of additive packages to meet future market needs and allow for the use of low viscosity lubricants in highly demanding downsized forced induction engine applications, without negatively impacting on protection and durability. Future design objectives are likely to include improved high temperature deposit protection for pistons, better sludge control and seal compatibility.

It may take some time for SAE 16 synthetic motor oil to find widespread use, but current synthetic engine lubricants still hold major advantages over regular mineral motor oils; however it’s important that you use a high quality lubricant such as that supplied by Habot Oil.