Extending engine oil drain intervals has typically required switching to a higher grade of oil or adopting an engine oil sampling and testing program. Now, for light trucks at least, there’s another method – letting the vehicle itself determine when the oil needs changing.

General Motors has been working on such technology since the 1990s, resulting in its patented GM Oil Life System (GMOLS), which the company said can double or even triple the time between oil changes compared to the standard 3,000-mile interval. The key, said Peter Lord, executive director for GM’s Service Operations, is using a computer algorithm that tracks engine revolutions and temperature to predict oil life based on these parameters and driver use.

“OLS, which is now on more than 95% of GM cars and trucks, ends the traditional 3,000-mile oil change by alerting you when the oil change is really needed – which could be anywhere from 3,000 to 10,000 miles,” added Brian McVeigh, gm of the company’s Fleet & Commercial division, during a special 2006 product preview GM recently held.

“There are roughly 20-million vehicles on the road today already equipped with this technology and these cars and trucks together can help save an estimated 120 million gallons of oil if drivers and fleet administrators simply follow the ‘change oil’ light recommendation,” he noted. “That really translates to everyone’s bottom line.”

“The technology is based on actual engine and operating data that calculates when the oil needs to be changed,” Joyce Fierens, GM’s director of fleet service, told Fleet Owner. “We feel it’s a great cost-saving opportunity especially for commercial fleets.”

Fierens said that, according to GM’s calculations, a fleet of 3,000 vehicles racking up 21,000 miles a year per unit could save $672,000 in engine oil, shop and labor time, plus vehicle downtime, by pushing the vehicle oil drain interval from 5,000 miles to just 7,500 miles.

“Obviously, the savings are dependent on how far you can safely extend the oil drain – and that wholly depends on the operational conditions and use patterns of the fleet’s vehicles,” she cautioned. “However, not every fleet operates in harsh conditions, so it doesn’t make sense to have an oil change schedule based on those conditions.”

GMOLS is also the cornerstone of GM’s new vehicle maintenance package, which it hopes will increase business at its dealership network primarily for those fleets that don’t have their own in-house maintenance resources.

Lord said GM’s new Simplified Maintenance Schedules (SMS) are a departure from the typical industry approach of basing maintenance intervals on mileage. Instead of following a list of different services to be performed at different mileage intervals, the program is based solely on the change oil light/message.

The first time the message on the dash appears, dealerships offer a Maintenance I service package which includes an oil and filter change, a four-tire rotation, visual inspections of the fluid levels and brakes and a resetting of the system, said Lord. The next time the message appears, a Maintenance II service package is recommended, which includes everything in Maintenance I, plus a professional inspection of the suspension and steering components and the transmission, he said.

After the first two visits, drivers will alternate between the two schedules as the prompt appears on the dash for the life of the vehicle. “SMS is a major convenience because it takes the guesswork out of when to change oil and it eliminates the need to make decisions regarding routine maintenance,” Lord said. He stressed, however, that engine oil and filter must be changed at least once a year even if the GMOLS indicator does not come on.