Doug McAllister/Under the Hood: Oil-change intervals

Longer oil-change intervals may not be the best way to go.

Many vehicle manufacturers have pushed the oil change interval out to 5,000 or 8,000 and even 10,000 miles. These higher intervals may not be the way to go based on some recent findings.

In one case the manufacturers’ standard oil-drain service for particular vehicles was scheduled at around 7,500 miles, but people following these recommendations were experiencing engine damage. Oil sludge was building up in the engine causing small oil passages to clog and engine parts to fail. The manufacturers extended the warranty on these engines but started requiring shorter oil-change intervals. We have seen several of these cases in our shops where clients let long periods of time go between oil changes, which caused the oil to sludge up in the engine.

One of the components that seems to be very susceptible to problems from oil sludge is the Variable Timing Actuator. There are very tiny passages in this component and if oil can’t get through, the actuator will stop working, the car will not run right and, in most cases, a Check Engine Light will turn on.

Oil sludge has become more of a problem over the last 10 or so years as a result of environmental concerns and tightened budgets.

In attempts to get fuel economy up, manufacturers are using smaller, more high-performance engines and they are running them hotter to burn fuel more efficiently. They are also requiring lighter weight oil and the combination of all of this is creating an environment where sludging can occur.

Another reason for a manufacturer to tout longer maintenance intervals is to be able to keep the projected cost of maintenance down on the vehicle, thus making the purchase price of a vehicle more attractive to buyers.

So what can you do?

First, beware of pushing your oil change interval out too far. Oil changes are cheap compared to having to do any kind of engine work.

Make sure the correct oil is used when you do have your car serviced. Make sure a synthetic blend or full synthetic oil is used.

If you are going to run longer intervals, use a full synthetic. Full synthetic oils are not prone to sludge and can perform well on longer intervals.

Remember, buyer beware. An inexpensive oil change may not include quality engine oil and a quality oil filter. Always ask before you have your car serviced.

Ÿ Douglas Automotive is at 312 S. Hager Ave., Barrington, (847) 381-0454, and 7218B Virginia Road, Crystal Lake, (815) 356-0440. For information, visit douglasautomotive.com. Send questions to underthehood@dailyherald.com.