Ive mentioned it often enough that GF-6 oils were originally supposed to be available in 2016. Right now, were on track for mid-2020 if the Sequence IVB can be squared away. The delay from tests being accepted to first license date is primarily due to rules established in the American Petroleum Institutes Engine Oil Licensing and Certification System (API 1509) regarding base oil interchange and viscosity grade read across. These procedures allow additive companies to develop additive systems for their customers without running every test on every base oil combination and every viscosity grade. The time and expense to do so would really make it impossible to develop any new engine oil category.

One of the drivers for GF-6 is the proliferation of turbocharged, gasoline fueled direct injection engines. Lubrizol cites automotive registration data showing that the United States had 25.5 million registered passenger cars powered by TGDI engines in 2016. This is up from about 6 million in 2011. In addition, projections indicate that by the year 2024, eight out of 10 cars produced in America will be equipped with TGDI engines. This train is on the fast track!

GDI and TGDI engines offer some very impressive fuel economy benefits and a lot of power in a small package. A four-cylinder TGDI engine can generate as much torque as a six-cylinder port fuel injected engine. There is a downside, though. TGDI engines operate in a much harsher engine environment that includes higher temperatures, higher cylinder pressures and slower operating speeds. The result is a phenomenon known as low-speed pre-ignition.

Pre-ignition is the technical term for engine knock. Engine knock is premature combustion of fuel and has historically resulted when fuel contains relatively low levels of octane or other low-molecular-weight hydrocarbons, which reduces the combustion level at which ignition can occur. Leaded gasoline helped prevent engine knock until the beginning of emissions controls. When we got the lead out, we had to essentially de-tune engines to accept lower octane fuels. Through modern refining techniques, weve been able to recapture some of the lost octane. With TGDI engines, we may be on the road to higher octane requirements.

In the meantime, the industry has developed a test to predict LSPI caused by engine oil formulations. The exact mechanism for oil-induced LSPI is not entirely clear, but is likely the result of oil getting into the combustion chamber and forming a hot spot on the surface. This spot becomes a secondary ignition source, causing the fuel to ignite prematurely. Some theories about oil-induced LSPI include additive chemistry issues (see Page 40 in this issue). One SAE paper suggests that calcium-containing additives may be more prone to LSPI than those containing magnesium. Oxidation inhibitors may need to be increased as well. Although LSPI may happen infrequently, it can be devastating to the engine.

The LSPI test, now known as the Sequence IX, was originally intended to be part of ILSAC GF-6, but due to the delays in category introduction, the test is now a part of the API SN Plus and API SN Plus-Resource Conserving supplemental category scheduled to roll into the market this month.

Lets move on to the status of base oils. When APIs current engine oil category system was first developed in the late 1960s, what we now refer to as API Group I base oils were all there was. While these oils were satisfactory for then-current engine oil formulations, they required a certain type of additive system. There was also wide variation in oil composition and performance between sources, though variations in additive chemistry could compensate for the base oil variations.

Additives provide the following to a base oil: modification of oil properties (think of viscosity index improvers or pour point depressants); protection of the base oil such as improved oxidation or foam resistance; and protection of the engine through antiwear, surface protection and anti-corrosion agents. Some additives offer improvements in more than one area. For some background on the subject, you can reference SAE J357, Physical and Chemical Properties of Engine Oils.

The first Group II type base oils appeared in the early 1970s and offered better and more consistent performance. They became more popular with engine oil formulators, since they included improved yields and fewer undesirable byproducts. Additive chemistries could now focus more on oil properties that aided engine protection and performance.

Later came Group III base oils, which are Group II on steroids. They are refined to such an extent that almost nothing but paraffinic hydrocarbons are left. They were a new class of base oil in the 1990s but only a niche product until 1998 when they were declared a synthetic in a National Advertising Division case between Exxon and Castrol.

As reported in the 2017-2018 edition of the LubesnGreases Lubricants Industry Factbook, in 2007 Group I base oils were 65 percent of the base oil market globally, with Group II at 19 percent and Group III coming in at 4 percent. Ten years later, Group I had dropped to 39 percent, while Group II and Group III rose to 35 percent and 13 percent, respectively. This trend continues, as almost all planned additions of base oil volume in the near future are for Group II and Group III.

These improved base oils offer advantages in performance properties, especially V.I. and volatility. Combined with improved additive chemistry, new engine oils are being developed that provide higher performance over longer drain intervals.

Naturally, original equipment manufacturers are taking advantage of these developments to get better performance for their engines. Durability is one feature that is of great interest to both OEMs and consumers. My trusty 2008 Nissan Quest recently turned over 130,000 miles on the odometer and doesnt seem to be in any danger of dying. In fact, I just had the oil changed, and when the technician brought the van around he commented that it was the cleanest car at that mileage he had ever seen! Thats a tribute to my wifes insistence on regular washing and vacuuming as much as getting the oil changed, but it does put a smile on my face.

The bottom line on passenger car engine oils is that API SN and SN-RC are the current standards, but API SN Plus and SN Plus-RC are about to come on the stage. Hard to say whether or not they will be making cameo appearances or whether they will stick around for a while. ILSAC GF-5 will continue at least until early 2020, leaning on API SN Plus to keep it going. That leaves GF-6 (API SP?) still to be heard from. Will it finally reach the market, or will the Sequence X chain wear test be tucked into API SN Plus and GF-6 consigned to the lubricants trash heap of history?

Stay tuned!

Industry consultant Steve Swedberg has over 40 years experience in lubricants, most notably with Pennzoil and Chevron Oronite. He is a longtime member of the American Chemical Society and SAE International, where he was chairman of Technical Committee 1 on automotive engine oils. He can be reached at steveswedberg
@cox.net.