passenger vehicles between the model years (MY) 2012-2016 and Phase II concerns MY 2017-2025. By the year 2025, passenger cars and light trucks must attain an average fuel economy of 54.5 mpg. Hence, the upcoming ILSC GF-6 standards will be very stringent to accommodate the Phase II goals. The need for continuous lubricant innovation is twofold. Firstly, lubricants must adapt to work with newer engine technologies. Secondly, lubricants themselves contribute to fuel economy. OEMs are exploring every avenue to meet the Phase II CAFÉ goals. Lubricants tend to improve fuel by only up to 3%, but with light-duty vehicles producing 60% of greenhouse gas (GHG) emissions from the U.S. transportation sector, there is huge GHG emission reduction potential.
Aside from legislation, advancements in engine technology require complimentary lubrication. In recent years, gasoline direct injection (GDI) and turbocharged gasoline direct injection (TGDI) have taken the market by storm. About fifty percent of all MY 2017 cars and light trucks have GDI technology, and that number is steadily growing6
.
Compared to traditional port fuel injector engines, GDI engines directly inject gasoline into the combustion chamber. The smaller form factor and better fuel economy are responsible for its popularity. TGDI engines are particularly fuel efficient because they introduce more oxygen into the combustion chamber. However, the higher performance and temperature may cause the engine oil to deteriorate faster. In addition, GDI engines are prone to more fuel dilution in the ring pack oil. Herein lies the need for improved engine oils over the GF-5 standard.
Now that TGDI engines have flooded the market, there is a pressing need to solve low-speed pre-ignition (LSPI). LSPI is an event in which combustion of the fuel-air mixture occurs, prior to the spark ignition, when the engine operates at low speeds and high loads. This phenomenon differs from conventional engine knock because LSPI is unpredictable and more damaging with potential piston cracking, but improvements to hardware design, fuel formulation, lubricant composition and engine control management strategies can curb LSPI4
. There are several theories trying to explain the cause of LSPI. One theory assumes that an oil droplet is expelled from the top ring groove, enters
the combustion, mixes with fuel, and prematurely ignites. Another theory states that piston deposits may be the cause of LSPI. Thus, LSPI prevention is one of the main objectives of ILSAC GF-6.
Another issue with TGDI engines is a high level of particulate matter. This is a shared characteristic with diesel engines because the fuel is directly injected into the combustion chamber. The soot production and oil degradation can lead to timing chain wear which results in decreased performance, higher emissions and possibly expensive repairs.
Thinning engine oils is an ongoing trend because of the fuel economy improvements. However, this trend causes some concerns. Temperature’s effect on viscosity is well documented. At operating temperatures, the engine is protected from friction and wear by a thin oil film. However, if overheating occurs, the thin oil film will degrade and potentially cause devastating wear to the engine. Another disadvantage of thinner oils is abrasive soot and wear debris particulate matter, equal to or greater than the thickness of the oil film, will cause wear4
. This puts
importance on oil filters to prevent wear debris from entering the oil film. As the thin oil trend continues, ILSAC GF-6 must implement standards that balance both engine performance and robustness.
ILSAC GF-6 ILSAC GF-6 addresses many issues over ILSAC GF-5. First and foremost, fuel economy and fuel economy retention are of paramount importance as Phase II CAFE deadlines are fast approaching. The popularity of TGDI engines calls for a focus on turbocharger deposit control, chain wear protection and LSPI prevention. Engine durability and wear protection for idle-stop will also be improved.
ILSAC GF-6 is the first ILSAC GF standard to have two subcategories: GF-6A and GF-6B. The two subcategories are mostly the same with one key difference. ILSAC GF-6A will be backwards compatible with GF-5, but GF-6B will not and will accommodate engine oils with viscosities SAE 0W-16 and lower. Overall, there is virtually no difference between GF-6A and GF-6B, aside from the slight increase in fuel efficiency in the latter subcategory. This is to be expected because low viscosity engine oils have proven to increase fuel efficiency.
Continued on page 46 LUBE MAGAZINE NO.153 OCTOBER 2019 41
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