Automotive Lubricants



There is an ongoing discussion in the oil industry that almost defies comprehension. It has generated more press than anything else I can think of, and I am guilty of participating. The issue: What is the proper oil drain interval for cars and light-duty trucks?

Let me explain why I have decided to bring this up again. I am on Facebook. Its a good way to stay in contact with family and friends who are remote from me geographically. Admittedly, there is a certain gossipy feeling about it and more than enough ads to keep me distracted. (My wife says that is not difficult.) So here I am, scanning the latest posts, and I see an advertorial by ExxonMobil for Mobil 1. It consists of a short video discussing how often to change your oil. The video was pretty straight forward, but what caught my eye was the fact that there were over 150 comments on it!

So what did the comments say? A few were of the read your owners manual persuasion. A few more said they follow their oil life monitor recommendation. One or two said over 25,000 miles. A fair number suggested that somewhere between 5,000 and 7,000 miles was their choice. However, the big winner was 3,000 miles or three months! Among the reasons given were my father told me, my mechanic told me, and Its cheap insurance.

Coincidentally, the Society of Tribologists and Lubrication Engineers monthly magazine, Tribology & Lubrication Technology, had an article on the stubborn adherence to a 3,000-mile drain interval written by its editor, Evan Zabawski. In it, he traces the history of oil change recommendations and how the driving public reacted to them. What he thinks is that belief in the 3,000 mile myth is based on one or more of the following ideas:

1. Oil degrades or breaks down.

2. Additives wear out.

3. Oil should always be changed at 3,000 miles.

4. Its cheap insurance.

I have to thank Evan for giving me the talking points I need to address and respond to Facebook readers.

The idea that oil breaks down is both true and false. If you think about it, base oil is subjected to some pretty high temperatures during the refining process. In fact, if it wasnt distilled under vacuum, it would become tar and of no use to anyone except road repair crews. API Group I base oils have historically been refined using fractional vacuum distillation followed by solvent removal of unstable components and wax. The problem with that is not all the bad actors are removed, and there is a significant loss of yield.

The development of Group II and Group III processes converted all the unwanted components into branched paraffins and naphthenes, which are actually more stable.

As an aside, in a famous decision by the National Advertising Division of the Better Business Bureau in 1999, API Group III was included in the list of synthetic base oils due to the fact that it could be produced either by synthesis or by refining. This has created a lot of confusion and distrust among consumers, some of whom believe that Group III is fake synthetic.

API Group IV is reserved for polyalphaolefin, which is truly synthetic. It is produced by connecting a relatively controlled number of 1-decene molecules to produce a fully saturated oligomer of a viscosity useful for producing engine oils. These are also very stable base stocks.

Base oils are, in fact, open to deterioration over a long drain interval, but thats where additives come into play. Engine oils are formulated from mostly base oil with a series of additive components, which do one of three things: protect the engine, protect the base oil or improve base oil properties. For example, antiwear additives protect the engine against wear. Protecting the base oil would be the job of antioxidants, and pour point depressants improve the cold-temperature properties of the base oil. The right combination of additives and base oil will create a finished engine oil that meets the test requirements of the latest API Service Category, SN Plus.

So will additives wear out? The brief answer is yes, but after a long time in service. In some tests, a good antioxidant will allow an oil to remain useful for several thousand hours. The crankcase of a gasoline- or diesel-fueled engine is a pretty messy place with water, exhaust gases, wear debris, corrosion byproducts and other chemical beasts mixed with the oil. Its actually pretty amazing how long the oil can continue to function effectively.

This leads to the third idea Evan listed, that oil should always be changed at 3,000 miles. Back on Facebook, several of the commenters said that their mechanic recommended it, and others noted that their father had recommended it. A brief tangent here: One of Pennzoils most successful ad campaigns was from long ago. It proposed that my father used it and his father had, as well. The tag line was Your Fathers Father … The point was, and still is, that recommendations by authority figures are powerful. You dont see very many ads that recommend reading your owners manual. (More on that later.)

General Motors Research developed the oil life monitor as a way to get more realistic oil change intervals. Basically, it counts the number of crankcase revolutions and compares it to the average engine oil temperature. These sensors use algorithms that start with the maximum interval that would be allowed if the vehicle operated at the optimum oil temperature and then subtract for deviations above or below that temperature. The OLM does not analyze the oil, only the operating conditions.

OEM recommended oil change intervals are now 7,500 to 10,000 miles, so 3,000 miles seems to be too conservative.

The final idea Evan pointed to was that its cheap insurance. Ive heard that from some people within the industry. It does have a powerful ring to it. An oil change using conventional oil runs around $35. If that oil change gives longer engine life, it really is cheap insurance. However, there are forces that are working against that idea.

The state of California went on a campaign a few years ago to extend the oil change interval to reduce the amount of used oil that needed to be disposed of or recycled. The state determined that 40 percent of oil used was lost due to combustion and leakage. They also determined that not all oil was disposed of properly.

They developed a website that showed what the oil change interval was for nearly every car or light truck. You could put in the year and make of your vehicle, and the website would tell you what the normal oil change interval was as reported in the owners manual.

To the legislators in California, it appeared that the 3,000-mile oil change interval was merely a way to sell more oil. There were lawsuits by motorists that felt that way. In fact, as a result of consumer and legislative pressure, Jiffy Lube, the largest fast oil change company, modified its change interval recommendation. I think its worth sharing:

Both vehicle manufacturers and the vehicle service industry agree that staying on-schedule with the owners manual recommendations is the best way to ensure youre changing your oil appropriately.

The manuals schedule includes recommendations about the best type of oil for your vehicle, whether its conventional, synthetic or a blend. The oil type will go a long way toward determining the interval range between oil changes.

While the rule to change your oil every 3,000 miles may have been true in years past, oil technology has moved well past it now. If you still follow this rule, the odds are you are changing your oil too frequently.

Were left with the same problem: When should I have my oil changed? To some extent, it is still personal choice. The cost of oil is minimal compared to the cost of even the most simple engine repair, so being conservative seems to be appropriate. Theres still the question of the environment and oil quality. Facebook readers have a wide divergence in views and oil technology is now so advanced that a cautious approach still allows for more miles between drains.

The bottom line is that engines are too costly to ignore simple things like oil changes and other regular maintenance. Take care of your customers vehicle, and it will return the favor with long years of life and a loyal clientele.

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, ASTM International and SAE International, where he was chairman of Technical Committee 1 on automotive engine oils. He can be reached at