There were a few original equipment manufacturer oils (Motorcraft, Mopar, Goodwrench) that address­ed some specific issues, but the most common reference was to API Service Categories MS, MM and ML. Viscosity was ruled by monogrades, although multigrades were beginning to make some significant inroads.

Do-it-yourself was also the rule. Estimates of up to 80 percent DIY were made back then, but only based on relative sales through parts stores versus dealers and garages. It wasnt until the early 1980s that fast oil change stores began to show up. The first one was in Colorado.

With the introduction of fuel economy requirements and emissions controls, the ballgame began to change. Fuel economy was primarily driven by viscosity. SAE 30 and SAE 10W-40 viscosity oils gave way to SAE 10W-30 oils. The first fuel economy test for oils was the Five Car Test, in which five different make and model cars were run on chassis dynamometers using the Federal Test Procedure vehicle emissions cycle, which showed how much fuel could be saved. The results were averaged over all five cars and often fell in the 2 percent range. The industry wasnt too thrilled with the high cost of the Five Car Test and began to develop an engine stand test that would be more reliable and less expensive.

Beginning in the 1980s, there was a move to segment the marketplace. This resulted in not only fuel economy engine oils but also pickup truck oils and SUV oils, to name a few. These oils were often higher viscosity, with SAE 20W-50 as a favorite, and promoted as the tougher oil for harder and more rugged driving conditions. They were also promoted as off-road oils.

Racing forward to today, I note that there are at least five general categories identified on page 10 of the Factbook. Conventional oils that are API GF-5 and SN are 64 percent of the market. The next most common oil type is the branded, top tier oil coming in at 10 percent of sales volume, while high mileage oils are at 8 percent. The remaining oils are lower API categories and mid-tier oils.

The most interesting part of this breakdown is the high mileage oil targeting vehicles with more than 75,000 miles on the odometer. The reasoning here is that seals have gotten harder and perhaps shrunk a bit, and there is wear, albeit normal, that impacts engine performance and engine life. These oils are formulated to fight leaks, deposits, friction and sludge. That means some additional seal swell agents, more dispersants, antioxidants and friction modifiers. Top tier oils have mostly become synthetic, using API Group III or Group IV base stocks. More about that later.

The other point about passenger car engine oils is the shift in viscosity weve seen over the last 35 years or so. Early in my career, I would regularly look at engine sales by viscosity grade. I was primarily interested in sales volumes, but over time I found that the shift in viscosity grade was even more telling.

The first year I began tracking data (from the discontinued National Petrochemical & Refiners Associations Annual Lube Oil Sales Report), the viscosity share breakdown showed a significant amount of monogrades. When the report finally died off, the monogrades were not even a blip on the radar and had been replaced by multigrades such as SAE 10W-30 and later SAE 5W-30.

Its pretty easy to see that the general trend is towards lower viscosity engine oils. Whats also interesting is that the volume of engine oils sold has stayed relatively constant, even though there are more cars and trucks on the road. Extended drain intervals are the reason. Where the 1980 numbers were based on 3,000 mile drains, which meant more oil was sold, by 2015 average drains had moved up to about 4,500 miles; vehicles with oil life monitors were at 6,000 miles.

Im sure you recognize that lower viscosity oils mean lighter base stocks are required. We all know the driving forces behind lower viscosity oils: fuel economy and lower emissions. The question is just how much lighter base stocks are now than in earlier years.

I took the data from my various charts, estimated a base stock viscosity needed for each finished oil viscosity grade and calculated an overall average or pool viscosity requirement for base stock. To the surprise of no one Im sure, the engine oil pool viscosity has dropped over 25 percent in the last 35 years. That means more light grades are needed. At the same time, refining techniques have created the needed lower viscosity cuts.

This discussion leads directly to the second item in my list, which is how base stock manufacturing has changed. When I started in the business, there were no real API Group II base stock manufacturers. Sinclair was hydro-finishing their neutral oils at their Houston plant. However, that didnt raise the saturates to the expected Group II level of 90 percent or greater. It wasnt until about 10 years later (1975) that Sunoco began producing hydrotreated base stocks at their Yabucoa, Puerto Rico, plant. These oils were solvent dewaxed and not catalytically dewaxed, so the saturates level barely made it past the magic 90 percent mark. The first true Group II plant was Chevrons Richmond, California, operation, which was introduced in the late 70s.

On page 28 of the Factbook, the change in North American base stock manufacturing is graphically shown. In 1998, Group II and III base stocks accounted for 21 percent of productive capacity while Group I was at 56 percent. By 2016, Group II was 52 percent and Group I was at 23 percent. If you recognize that the cost of a change like this is very high, this represents quite a reversal in 18 years.

Meanwhile, a debate had started over just what defined a synthetic base stock.

I was chairing SAEs Technical Committee 1 on engine oils in the early 1990s. A seemingly innocuous revision of SAE J357, Properties of New and Used Engine Oils, opened a giant can of worms over the definition of synthetics. On one side, the polyalphaolefin manufacturers were saying that they had the true synthetics because they manufactured base stocks from monomers of decene (and some dodecene as well). On the other side were the oil refiners who said that, while their hydroprocessing created very high viscosity index materials (API Group III), they could also be made using a wax polymerization process, so Group III was synthetic as well.

The SAE folks could never come to a consensus on this issue, and gave it up finally. API also had struggled and came up with the five group system we know today. It is based on chemical and physical properties of the base stocks rather than manufacturing processes. The final word on synthetics came in a U.S. National Advertising Division of the Council of Better Business Bureaus decision in 1998, which sanctioned calling Group III base stocks synthetic.

Now that Ive wandered through the weeds, Ive circled back to my original point, that is, the LubesnGreases Lubricants Industry Factbook is a valuable source of information for our industry and is also a great starting point for any industry history buffs out there. Read and enjoy!

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.