Automotive Lubricants



© SlobodanMiljevic

Making an Engine Oil

Every time you purchase or install a quart of engine oil, you are the end point of a manufacturing chain that includes oil, additives, containers and other assorted functions that are all designed to get the products you need for your vehicle. In addition to engine oil, there are various other lubricants that are needed for your car’s proper operation. Among these are transmission fluids, greases and gear oils. The engine oil portion is one of the most crucial and is the one I’ll address in this column. Remember that similar processes are also part of the other lubrication products.

First a special word about quality. I’ve written before about various aspects of quality, including quality control, quality assurance, quality inspection and quality protection. Quality is the root of all good oil products. If any one of these parts is neglected, there will be problems.

Let’s begin with the most fundamental of all: base oil. I’m sure all of you are aware of the base oil grouping system employed by API. Five groups encompass all the lubricating oils used by oil marketers. In general, the categories, starting with Group I though Group III, are petroleum-based and increase in quality. Group IV is a specific synthetic: polyalphaolefin. Group V is essentially everything not defined in the first four groups. There have been discussions about expansion and rearrangement of the various groups, so this system is certainly not cast in stone. It’s what we work with at present.

Refinery processes as well as crude sources determine which crude-sourced base oil group is produced. Briefly, Group I typically uses classic solvent refining techniques with higher quality crude sources. Highly paraffinic crudes, like Pennsylvania crude, can be processed very effectively. Groups II and III employ hydrogen processing techniques to convert more asphaltic aromatic and naphthenic crudes. The level of treatment determines whether it is a Group II or Group III base oil. Group III, because of its level of treatment and general properties, has been designated as “synthetic” and is the most common base oil type used in motor oils claiming partial or total synthetic properties.

Additives are an essential part of a modern engine oil. Base oils constitute about 85%-90% of the finished oil. It’s actually more than that, since the additive components are all diluted with base oil. The additives are a cocktail of chemicals that are designed to do one or both of these things:

1) Enhance the existing properties of the base oil. These include, among other things, oxidation resistance, viscosity, and temperature properties or low-temperature performance. 

2) Impart properties that don’t naturally exist in the base oil. Anti-wear, anti-foam, dispersancy, and detergency are well-known examples.

Additives are the bailiwick of the chemical companies that develop and test components as well as combinations to see if they can provide enhancements to any given requirement. The additive systems are selective and are developed for a particular base oil group. They do this first on a bench test basis (test tubes and lab glassware). Once they find a promising combination, they turn to the engine tests to prove performance.

The engine tests demonstrate actual field performance, which has been defined by the original equipment manufacturers. The engine tests are developed within ASTM Committee D02 and are the result of cooperation between OEMs, chemical companies, test laboratories and oil marketers. All of this is described and managed through the Engine Oil Lubricant Classification System (API 1509), now in its 20th edition.

OK, so now we have appropriate base oils and additives that have been tested and demonstrated to meet industry requirements. What’s next?

We go from the lab and the engine tests to actual manufacture of finished oils. Basically, it’s done one of two ways. The first is in a batch process, which includes blending a particular viscosity grade in a blending vessel, testing to be sure it meets specifications, like viscosity and additive treatment levels, and then to a finished oil tank ready for filling. The other way is using inline blenders. This process involves a series of meters that add the proper amounts of each base oil and additive to a stream that goes either to a finished oil tank or directly to the packaging line.

At the packaging line, the finished engine oil is measured into the appropriate container. Oil is always filled by weight. Why, you ask? Packaging laws define volume by weight of the oil, and there can be severe repercussions if the oil advertised on the label is not what is in the container. That goes not only for quantity level claims but also for viscosity and additive treatment levels. 

An interesting sidelight to the packaging story is that for large blenders, the weight of the container—especially 1-quart bottles—can be extremely expensive. When I worked at Pennzoil, we started our plastic bottle filling using the classic side neck design. There was a lot of concern about storage and whether 1-quart bottles could be stacked three pallets high in the warehouse. That’s not a small issue when you are filling about 250 million bottles a year!

We tested bottle weights and carton designs in an effort to provide satisfactory strength in the most cost-effective way. As I remember it, the first bottles weighed 53 grams. The cost of HDPE last year was about $0.40 per pound. For 250 million 1-quart bottles at 53 grams per bottle, the cost would be $11.7 million just for the plastic. After about two to three years, we were able to reduce the weight of each bottle to 49 grams without sacrificing bottle integrity or load-bearing strength. The savings to Pennzoil was nearly $1 million per year.

The next step in the trip to the market is transportation. Because engine oil can be sold either in containers or in bulk, it can be transported in tank cars and tank trucks as well as in non-tank trucks and railcars. Each shipping method has different quality assurance criteria. 

We’re getting close now. When the oil is delivered to the local distributor or jobber, they become responsible for protecting the integrity of the finished oil. Cases of quarts are stored in the warehouse, stacked on pallets. Drums are stored under cover from potential adverse weather or with the drum tilted to keep water from getting into the oil and contaminating it. Bulk oil is stored in a properly vented, weatherproof tank. There it sits, waiting for someone to purchase it for their auto parts store, big box store, garage or quick lube.

The final step in this odyssey is the order to deliver to your friendly source where it will finally be ready for installation in your vehicle. At the big box or auto parts store, you do-it-yourselfers will pick up 4 to 6 quarts of the recommended oil, probably an oil filter and any other desired tools to do the job. 

“When the oil is delivered to the local distributor or jobber, they become responsible for protecting the integrity of the finished oil.”

Don’t forget to properly dispose of the used oil. Where should that be? Probably at a nearby quick lube or garage where used oil is stored in a tank or drum until it can be picked up by an oil rerefiner. 

If you would rather be a do-it-for-me consumer, you could take your chosen oil to a local garage or quick lube and have them install it. After all, they have the tools and the skills to do the job for you. Even better, just take your vehicle to those same locations and let them install the proper oil. You get the benefit of their skills and their bulk oil system (or specialized oils). No fuss.

So, there it is! The saga of an engine oil from the well, through the refinery, chemicals selected and evaluated in the test labs, sold to the oil marketer, blended, shipped, stored and finally into your crankcase, where it will serve to protect your very expensive investment for about 5,000 to 10,000 miles before the process is repeated.

I’ve been a part of this industry for a very long time, and it never ceases to amaze me that this process works with such a low level of error. It’s a tribute to the men and women who work so hard to get it right. A tip of my hat to all.

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