Automotive

At the same time, new regulations regarding fuel economy were passed. The net result was a de-emphasis on horsepower and engine displacement. Incidentally, improvements in fuel economy were only partially due to the oil embargo; it also had a major impact on emissions. The 1970s saw the introduction of such exhaust emissions controls as catalytic mufflers and the removal of tetraethyl lead from gasoline. This caused a reduction in compression ratios, since no TEL meant more knock.

By 1980, average horsepower had dropped by 25% from 1975 levels. Fuel economy had begun to increase with a target of meeting the corporate average fuel economy (CAFE) of 27.5 miles per gallon, mandated by federal law by 1987. That was an amazing feat, since it meant that CAFE had been increased by nearly 75% from the 1975 base case.

What was happening to engine oil during this time? There had been several attempts at developing a system of engine oil quality designations going all the way back to 1911 when the first iteration of SAE J300 viscosity included some physical and chemical properties. However, the system we now use—API S categories—was first introduced between 1969 and 1970. The first generally recognized engine oil category was API SE, which was good through 1979. The engine tests were designed to provide wear, rust and deposit limits, which would define minimum oil quality. The “King of the Road” engine oil was SAE 10W-40. Then came the fuel economy and emissions limits, which forced the reduction in viscosity to SAE 5W-30. There were no established chemical limits. The API SF category came into being with somewhat more restrictive engine test requirements.

The latter half of the 1980s included several changes in oil categories, all aimed at fuel economy and emissions control as well as changes in engine test hardware. Fuel economy was first tested using a five-car test in which five vehicles were operated on a chassis roll dynamometer through specific driving cycles (the federal test used for determining fuel economy in mixed driving mode). The five cars were representative of the major North American OEMs’ best sellers. Each vehicle was first tested with a reference SAE 25W-30 and then run with the candidate oil. The difference was measured and reported.

Meanwhile, there was growing frustration by the OEMs that the category changes were not addressing their needs. This frustration surfaced at an SAE Fuels and Lubricants meeting in Portland, Oregon in 1988. The OEMs presented an engine oil specification and indicated that they would begin using it as their engine oil standard. After three to four years of negotiation, API and the OEMs created a new system, which we now know as API 1509, Engine Oil Licensing and Certification System. In addition to API and the OEMs, now known as the International Lubricants Specification Advisory Committee, the American Chemistry Council and ASTM became more directly involved. Of course, API represents the oil industry, ILSAC represents the automotive OEMs, ACC represents the additives industry and ASTM is responsible for the development and maintenance of the tests (both engine and bench) that define the categories.

Once the EOLCS was established, new categories could be developed with the assurance that there was general agreement by all parties that the tests and test limits were descriptive of the engine oils required by ILSAC member companies. 

Since then, there have been six iterations of engine oil categories designated as GF-1, GF-2, GF-3, GF-4, GF-5 and GF-6. The last and most current oil category, GF-6, has two subsets: GF-6A and GF-6B. The development and introduction of GF-6 took almost ten years. Formerly, the spacing was more in the five- to seven-year timeframe. Why did it take so long? It was a confluence of new tests and revisions to established tests as well as unforeseen occurrences along the way. Of the nine engine tests included in GF-6, only one was unchanged: the Sequence VIII. Three tests were new to the category: the Sequence VIF, the Sequence IX and the Sequence X. The Sequence IIIH, the Sequence IVB, the Sequence VH and the Sequence VIE involved changes in hardware and procedure. GF-6A and 6B were activated in May 2020. GF-5 was declared obsolete one year later in May 2021.

That’s a very long introduction, but hopefully it will make it clearer that changes, while needed, are thought through on a very deliberate basis, and test development can weigh heavily on timing. As of the date I am writing this, no one has brought out any ideas about the shape of the next category. The designation GF-7 does not even exist, although it is widely used as a focus of future developments. I’ll call it GF-7 for the sake of brevity, but in no way has the term been officially defined.

So let’s start by identifying some of the properties of earlier categories and where they may lead for GF-7. First, there is little doubt that viscosity will continue to be reduced. As was proven early on, lower viscosity means less friction, and that means better fuel economy. Discussions among the various players have suggested that SAE XW-8 and SAE XW-12 could very likely be added to the mix. Those grades are being used in Japan, so they are very likely to be included in GF-7. 

The reduction in viscosity will bring about an increase in volatility, which is another important property. Unfortunately, ILSAC wants to reduce volatility. The current GF-6 calls for volatility limits of 15% maximum, and there are thoughts that GF-7 may be limited to 13% maximum. If that is the case, it’s likely that the lower-viscosity grades may have a large proportion of synthetic base stocks and may even be totally synthetic. 

Fuel economy will be front and center, with the low-viscosity oils calling for even greater reductions versus current products. There are already chemical components in finished oils designed to reduce friction. These chemicals may be increased or new ones added to get better fuel economy. This will also probably mean a revision in the Sequence VI test or the adoption of another test, like the Toyota fuel economy test, to accommodate the lower viscosity, just as the Sequence VIF was added to handle SAE XW-16 in GF-6.

Another driver for synthetics is the high temperature, high shear viscosity, which is part of the SAE J300 viscosity standard. The very low SAE XW-8 and SAE XW-12 will have a minimum requirement that will likely mean synthetics.

Oxidation resistance and deposit control will be at least as good as GF-6. Again, the use of synthetics will assist in any improvements that will occur. It’s likely that there may be new or revised test procedures to measure these important requirements. The Sequence VH is likely to be replaced, since the engine hardware will be depleted by the time GF-7 is introduced.

The Sequence IX is a deposit test designed to measure the influence of oil in the combustion chamber of direct fuel injection engines. Oil in the combustion chamber can cause pre-ignition to occur. The current test in GF-6 uses new oil to measure the tendency to cause engine knock. ILSAC has already called for a used oil version of Sequence IX. This particular test may be added to GF-6 before GF-7 is introduced.

Wear resistance is always popular and will be addressed. GF-6 has a phosphorus limit of 0.06%-0.08%. This is for emission system protection but has an impact on wear protection. I’ve had conversations with several people and a stray thought was tossed out about wear as it relates to hybrid engines. When a hybrid starts out the day with a full charge, the battery drives the vehicle. As the battery runs down, a point is reached where the internal combustion engine takes over. Since I don’t have a hybrid, I can only imagine what happens. When the ICE kicks off, the engine must have some sort of shock load on the piston and main bearings. I don’t know if that is abrupt or even very harsh, but the thought has occurred to me that there may be some need for additional load-carrying capabilities that are not evaluated by any of the current engine tests. 

So GF-7, which doesn’t exist at this time, may be targeted for introduction in 2027. It will probably not be quite as extensive an upgrade as GF-6 was from GF-5, but there are a lot of issues that do need to be discussed and potential upgrades made. That’s par for the course in engine oil category developments.  

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