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I own a new truck which has a long service interval for the engine oil and filter. It has an oil change indicator display in the information cluster, which doesn't call for a change until 12,000 km or so. I've been changing the oil at 5,000 km, when it gets close to showing 50 per cent. I use the OEM filter with synthetic oil I purchase at the local parts place . Am I doing any damage by shortening my interval to match my comfort level? Also, am I wasting money replacing oil and filter unnecessarily early? – Don

When it comes to oil, change for change's sake won't hurt your car, but it will needlessly hurt your wallet.

"Changing the oil early is not a problem and doesn't hurt anything, but there's really no need to do it," says Kristin Huff with Blackstone Labs, a private oil analysis lab in Fort Wayne, Indiana. "Modern engines can run the oil a lot longer than engines could years ago."

Most auto makers call for oil changes at either 12,000 km or 16,000 km, and some can go as long as 24,000 km between changes, says

For plenty of new models, oil life monitoring systems have replaced guidelines in the manuals, so instead of calling for oil changes at set times, your car will tell you when it's time for an oil change.

Signals for change

There are two types of systems.

Some, like GM's system, use math. The computer puts engine revolutions, engine temperature, and miles driven into an algorithm and figures out when you have to change oil.

"Based on our analysis and the algorithm which takes into consideration driving habits, the customer would probably see his oil life monitor require a change anywhere from 5,000 to 12,000 kilometres," says Faye Roberts, GM Canada communications director in an email. "If he is changing his oil at 50 per cent life, the oil change is being completed before its useful life has come to an end."

The other type of system uses sensors to analyzes the oil itself.

"Oil life monitors vary in their accuracy," Huff says. "They tend to get better as time goes by."

No matter which system your vehicle uses, changing oil sooner than you need to isn't better for your car. And it's a waste of money and oil, Huff says.

Oh, and don't rush to get an oil change just because you've checked the oil and it looks dark.

"The oil has three jobs: to clean, to cool, and to lubricate the engine," Huff says. "All three of those things will cause it to oxidize and get dark, sometimes almost as soon as you put the oil into the engine."

If you have questions for Jason Tchir about driving or car maintenance, please write to

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