DETROIT -- General Motors is warning owners of almost 800,000 2010-12 vehicles that they may need oil changes more frequently than their onboard oil monitoring systems are telling them.
After high warranty claims on several models with four-cylinder engines, GM will reprogram software to make oil change warning lights go on sooner.
The change only affects 2010-2012 Chevrolet Equinox, GMC Terrain and Buick LaCrosse and Regal models with 2.4-liter LAF and LEA four-cylinder engines.
GM sent letters asking 778,956 owners of those vehicles to take them back to dealerships. The service will be done at no charge until Feb. 28, 2015.
"Even if they were out of warranty, they would still be good to have this done through that period," said GM spokesman Alan Adler. "After that, the dealers have discretion to make the customers happy."
The program involves vehicles in the United States as well as any affected vehicles that were exported.
"It is a U.S. program but exported vehicles would be treated the same," Adler said.
Adler said the changes resulting from the software reprogramming would not be dramatic.
Owner's manuals say the engine oil and filter must be changed at least once a year. Further guidance appears on a display screen that expresses remaining oil life as a percentage. Driving style and environment play a role in the readings.
GM began updating the software in December after noticing warranty claims for worn-out balance chains. The chains link the crankshaft and the balance shaft -- "just like the chain on your bicycle goes from the pedals to your back wheel" -- and make noise when they're worn, Adler said. The company declined to disclose the number of claims.
Product investigators found that recalibrating the oil-life monitor will help the chains last longer, Adler said.
The monitor "tells you when you should change your oil. It might be 5,000 miles, it might be 7,000 miles. It's going to vary based on how you drive your car," Adler said.
"Those intervals between oil changes were longer, but now they're going to be a little shorter because we have to find the right balance between how long the parts last and how much lubricant the vehicle needs."
Adler said the program is not a recall because it does not involve a safety issue.
Clarence Ditlow, executive director of the Center for Auto Safety in Washington, said a safety recall never expires, as opposed to the limited time frame of a voluntary equipment-modification program that does not involve a safety issue.
Said Ditlow: "A customer satisfaction program is something that each manufacturer at its discretion decides to implement."