Confusing claims from dealers, mechanics and oil companies can have you asking, "How often should I change my oil?" The real answer depends on a number of factors like mileage, time between changes and the type of oil in your car.

Scheduling Your Oil Change

Although the old adage "3,000 miles or 3 months" is still floated (mainly by oil and oil service companies), service manuals for newer vehicles specify an oil change at 5,000 to 7,500 miles. Of course, these numbers apply to cars that are driven under "normal driving conditions. Many factors can shorten or extend the rate of oil change.

Here are a few:

Oil type. Although conventional oil is the established leader in motor oil sales, synthetic oil has a number of compelling advantages that can offset its higher cost. Synthetic oil can last two to three times longer than conventional oil, while providing superior heat protection and cold weather viscosity.

Moisture burn-off. As your engine heats and cools, condensation can form inside. Running your engine generates heat and as the oil temperature rises, it can burn off the moisture that accumulates. If you use your vehicle mainly for short trips (especially in cold weather), the oil temperature can't become high enough to burn off moisture. In these situations, changing oil more frequently will help remove accumulated moisture and help avoid future engine corrosion problems.

Filtration efficiency. On of the biggest problems with used oil is that it collects contaminants over time. Most oil filters are designed to trap particles larger than 40 microns. A paper by the Society of Automotive Engineers, however, reports that engine damage can be reduced by 50% with a high efficiency filter that traps particles larger than 30 microns. A high efficiency filter can help extend the life of your motor oil.

One reason to change oil often. Although modern engines and oil formulations can double or triple the typical time between oil changes, there is one good reason to adhere to the "3,000 or 3" mantra: an oil change is like a check-up for your car. By bringing your vehicle in four times a year, you give a mechanic a chance to look at your car and help you head off minor maintenance and repair issues before they become major headaches.