Driving green means not changing your oil until you need to

When was the last time state tax dollars went toward telling you not to do something?

Ads against drunk driving, certainly. Perhaps ads against smoking cigarettes.

But now, California is embarking on a campaign to persuade its citizens not to change their oil so much.

More modern motor oils, better control of the combustion process through vastly more powerful electronic circuitry, and the persistence of generations-old auto advice have combined to lengthen oil-change intervals.

Yet many of us change our oil more often than we need to.

In California, in fact, roughly half of all drivers change their oil every 3,000 miles—or even more often!—despite manufacturers' recommended intervals for new cars that may be a multiple of that number.

And that, says California's Department of Resources, Recycling and Recovery, wastes oil that could potentially have a far longer life.

According to a story in the Los Angeles Times, the department has launched an ad campaign to encourage owners to be aware of the recommended oil-change interval for their car.

The tagline "Check Your Number," is also the domain name for a website that links owners to a website that gives the the carmaker's recommended interval—these days, often 7,500 to 15,000 miles—for their specific vehicle.

That links to some general advice about what the number means, along descriptions of unusual driving patterns that might require more frequent oil changes. Other more standard advice: Keep your tires properly inflated and switch off the engine if the car is stopped for more than a few seconds.

If every driver moved to the recommended oil-change interval, says a department spokesman, 10 million gallons of engine oil could be saved each year.

The change might as much as halve the amount of money drivers spend on oil changes, which cost $25 and up at quick-change facilities and potentially more at dealerships.

While green concerns aren't necessarily top of mind for many car owners, even in California, the economic argument will likely resonate with lots of people feeling the pinch of the three-year-old recession.

In other words, it's a win-win situation: Driving green means only replacing your engine oil when you really need to, and that saves you money.

Even the shrillest talk-radio hosts may find it hard to fight that one—though we have a sneaking suspicion they'll try anyway.