So what is all of this about? Why are longer drain intervals such a popular subject and one that raises so many different viewpoints? What are the opportunities and pitfalls that may be out there? Where are we now, and what direction does it look like were going? I hope to be able to shed some light on the subject.

Longer drain intervals are becoming the norm in the U.S. marketplace. This is one result of a shift in consumer practices from do it yourself (DIY) to do it for me (DIFM) behavior. The age of the backyard mechanic is going away. A lot of this is due to the increased complexity of modern automobiles. There are no more distributors, carburetors and easy-to-reach spark plugs to change. There is also the unpleasantness of crawling under a very low-slung vehicle to drain your oil and change the oil filter in order to add new oil. Instead, we have computers (with more computing power than the Apollo moon mission vehicles), fuel injectors and engine compartments so cram-packed with hardware that there is barely room to check the oil level, let alone do any significant maintenance.

Then theres the issue of what to do with the used oil. While DIYers can take their used oil to almost any garage, quick oil change facility or service station for disposal, the fact is that many do not. Instead, much DIY used oil is disposed of on the ground, down a storm drain or in the trash.

It is estimated that up to 80 percent of used oil generated by DIYers is disposed of improperly, a 2006 report from the U.S. Department of Energy stated – some 348 million gallons a year. There is a certain segment of the consuming public that is not convinced that the small amount of oil they dispose of is significant enough to cause serious ham to the environment, it added. Longer drains reduce this volume of used oil.

Supporting Data

The trend to increased oil drain intervals has been going on for many years. Normal drains went from 2,500 miles in the 1950s to 7,500 miles in the 90s. In recent years, oil drain intervals for driving classified as severe service have also increased. The table on page 6, from USA Today, shows the current recommended oil change intervals for most vehicles sold in the United States. Note that many automakers have installed indicator lights to alert drivers its time to change the oil.

Meanwhile, the direction of ILSAC/Oil – the joint automotive and oil industry group that develops engine oil specifications – continues towards hardier oils. Every reiteration of this groups GF-series of gasoline-fueled engine oil categories has called for more robust engine oils. At the same time, limits on oil volatility and performance in critical engine tests have become more rigorous. Obviously, these requirements have made longer drain intervals more obtainable.

Engine durability is the obvious driving force behind extending oil change intervals. Before the OEMs can make an oil drain recommendation, they must have data to support their decision. The only legitimate way to collect data is through field tests. All of the OEMs have done and continue to do extensive field testing. In addition, many oil and additive companies also run field tests to validate the performance of finished oils and additive systems.

One such test was reported at the SAE Fuels and Lubricants meeting in 1999. Its goal was to see how oil volatility might affect extended drain service. The paper, SAE 1999-01- 3469 by Alex Boffa and Greg Cook details a grueling New York City taxicab fleet test run by Chevron Oronite. The field test program was run using 1995 Chevrolet Caprices with 4.3L V-8 engines, which were run either on 10,000- or 20,000-mile drain intervals for a total of 105,000 miles. Four SAE 5W-30 oils of varying volatility were tested, each running in three engines for a total of 12 vehicles (see table, above).

Over the course of the test, regular oil samples were taken and various parameters were recorded, including oil consumption, top-offs and additive depletion. At the conclusion of the test all 12 engines were rated for sludge, varnish and wear.

The conclusions from this test are of some interest.

1. Higher oil consumption by Oils A and C – mostly due to base oil volatility losses – resulted in some additive concentration for both.

2. Higher oil consumption by Oils A and C also resulted in significant viscosity growth, which was even more pronounced for the 20,000-mile drain interval oil (C).

3. Lower oil consumption by Oils B and D resulted in some additive depletion for both.

4. Higher oil oxidation and poorer engine cleanliness and wear in the lower-volatility oils (B and D) were at least partly the result of the observed additive depletion.

5. For severe-service extended drain applications, oil formulations will require both good oil volatility and sufficient additive treatment in order to protect engines.

Of course, this field test program was run 10 years ago, using SJ formulations; since then, oil formulations have become even more durable, with more attention to wear protection and deposit control. Certainly, oil volatility remains a concern, so evaporative loss for todays GF-4 oils is set at a maximum 15 percent.

Other studies have shown that additive depletion occurs at a steady rate, and by 3,000 to 6,000 miles results in decreased oil oxidation resistance. Oils also demonstrate oxidation and nitration, resulting in viscosity gains. The implication is that excessive oil drain intervals may result in loss of fuel economy performance as well as increases in emissions. Properly formulated oils can achieve longer drain intervals – with an emphasis on properly formulated.

Where to Now?

There is no doubt that a longer drain is a fact in the marketplace. The OEMs have determined that their newer vehicles can operate successfully at drain intervals much greater than the traditional 3,000 mile or three months mantra long urged by the oil industry and fast-lube industry. However, that doesnt mean that they are being dishonest. There are many vehicle owners who believe that a 3,000-mile interval is insurance against any potential oil-related failure – a position strongly promoted by oil marketers and fast lubes.

Its a position not just accepted by the general public. Oil and additive industry professionals also support it. In the Aug. 1, 2007, issue of the Boston Globe, Dewey Szemenyei, marketing manager for passenger car motor oil additives for Afton Chemical Corp., said that he still changes the oil in his 1998 Toyota Sienna every 3,000 miles.

I really feel its great insurance, Dewey said, adding that if you go with the owners manual recommendation, you should in general not have any problems.

When you examine the annual sales of engine oils in the United States, the longer drain behavior of automobile owners seems to be reflected in the fact that gasoline engine oil sales peaked about five years ago and are on an ever-so-slight downward track. Theyve edged down by 1.2 to 5.8 percent every year since then. The 2007 sales volumes should be available from the National Petrochemical & Refiners Association next month. It will be interesting to see if the contraction in sales continues.

On the whole, the market definitely is going towards longer drains. The automakers and the consuming public are seemingly in accord that longer drains are right and the wave of the future. Going with the OEMs recommended drain interval is the right choice. It offers protection and environmental correctness.

Drivers who choose to go much further than OEM recommendations should carefully weigh the risks versus rewards of such actions. Before you decide to go 25,000 miles between drains, you should make sure that the oil you choose has been thoroughly tested and proven. Remember, an oil change costs about $30; a new engine considerably more.