Maximizing cost-effectiveness of maintenance costs is an important goal for any fleet manager. Of all preventive maintenance procedures, oil changes are the biggest expense. Every vehicle, regardless of type or application, must have regular oil changes in order to remain in sound running condition. The real question is which interval will work best for the vehicles in your fleet. Finding that answer can sometimes be a confusing search.

In recent years, extending oil change intervals has been an important objective of the world's leading automakers, which has resulted in increasingly stringent oil performance specs. According to General Motors' Mike McMillian, "There is technology available to raise the standard and extend the drain interval without compromising engine durability or removing the performance cushion."

Starting with the 2000-model year on certain vehicles, GM will raise the maximum mileage allowed between oil changes for Oil-Life monitor-equipped vehicles to between 10,000 and 15,000 miles, depending on vehicle brand and engine. Other manufacturers, such as BMW, have adopted similar policies.

As the recommended intervals change, most fleet managers will likely follow suit, though it may take some time. Most fleet managers keep their oil intervals within the manufacturer's guidelines; most change oil more frequently to reduce wear and tear.

"Oil changes are the cheapest form of insurance," said Carol Ann Bakeman, who manages a fleet of approximately 100 vehicles for the architectural firm of Daniel, Mann, Johnson, & Mendenhall. All the company's vehicles receive oil changes every 3,500 miles, which is significantly less than the manufacturer's suggested intervals. "It's better to err on the side of being too cautious," she surmises. Others in the fleet industry are also circumspect about these increased intervals.

"Some manufacturers have increased the recommended interval to 7,500 miles or more, but I would not feel comfortable pushing it that far," said Bob Brown, manager of vehicle fleet business and operations for Xerox, who oversees 10,500 vehicles, mostly vans. Currently, Xerox changes its vehicles' oil every 5,000 miles.

An important factor to consider when choosing the oil change interval for your fleet is the type of driving your drivers do. Stop-and-go driving, and hauling cargo, in particular, cause oil to break down more rapidly than normal driving. Consequently, oil changes for these vehicles need to be more frequent.

"When you do stop-and-go driving, or anything that's hard on the engine, you would be best off changing your oil more often than the manufacturers suggest," said Ray Scippa, manager of media relations for Pennzoil. "It's like an insurance policy," added Scippa.

With all the conflicting views on the subject, it still boils down to the fleet manager's decision as to what's best for his or her fleet's unique circumstances.

"There is a wide range of mileage intervals between different fleet managers," said Stan Leibowitz, fleet manager for Matshushita Corp. of America. "If you ask a fleet manager from the old school, they would change it every 3,000 miles. Some fleet managers now would follow the manufacturer's recommendation of 7,500 miles," Leibowitz said. Currently, Matsushita's vehicles undergo oil changes every 5,000 miles: 4,000 miles for drivers who do a lot of stop-and-go driving or highway driving.

The oil change interval you choose for your fleet could save a significant amount of money, particularly for larger fleets. For example, changing from 3,000-mile to 5,000-mile intervals for a fleet of 1,000 vehicles would vehicles would potentially save $40,000 per year.

Whatever oil change interval you choose, under no circumstances exceed the manufacturer's recommend interval. Doing so voids warranty coverage in the event of a malfunction, which could be a very expensive proposition.

GM Oil-Life System Takes the Guesswork Out of Oil Changes

Over the next five years, General Motors will equip almost all of its North American lineup with a patented new oil monitoring system that indicates when it's time for an oil change.

The GM Oil-Life System, which is already in use on some GM models, uses an indicator light to signal the driver that an oil change is needed. This system is intended to eliminate unnecessary oil changes, which waste oil. GM estimates that this system could potentially conserve nearly 40 million quarts of oil annually.

The patented engine oil-life monitoring technology involves computerized monitoring of engine revolutions, operating temperature, and other factors to determine when a vehicle's oil should be changed. Rather than depending on fixed oil change schedules that may not be suitable for all situations, the monitoring system customizes oil change schedules based on a vehicle's engine and transmission type, as well as an individual's driving habits. When the system senses that the oil in a vehicle is nearing the end of its useful life, it notifies the driver that an oil change is needed with a "change oil" dashboard message that's displayed for 15 seconds when the engine is started. Once an oil change is completed, the oil life monitoring system can be reset to begin a new analysis cycle.