Dear Tom and Ray:

Here is an odd thing: My brother, who lives in Germany, was shocked when I told him that here in the United States we change oil in a car about every 3,000 miles or three months. He told me that is crazy, crazy, crazy. In Germany, he says, NO ONE changes oil more than once a year, if even that. He's being serious, too. I double-checked with my dad, and it seems true. (Perhaps it's just my family being ultra-lazy or eco-sound?) However, if it's true, why are Americans changing oil so much more? Is this a case of the oil/mechanic industry making sure it has plenty of business at the cost of the consumer and the environment? Or is this really better for the car? Perhaps climate or something specifically different between the United States and Germany makes it necessary to change oil so often here? -- Anne

TOM: Well, some of it's just cultural differences. In some countries, people like hot dogs and baseball games. In other countries, they like bratwurst and wearing steel-plated, conical bras while singing opera. Go figure.

RAY: There actually are reasons why motor oil is changed less often in Germany. First of all, they drive fewer miles per year then we do. We, in the United States, average about 15,000-20,000 miles a year. Germans average about 10,000 miles a year.

TOM: Synthetic oil is also more popular there. And synthetic motor oil only needs to be changed every 10,000 miles, which works out to about once a year for the average German driver.

RAY: Finally, changing the oil is more expensive in Germany, which discourages people from doing it more often than necessary. Here in the states, an oil change for a four- or six-cylinder engine runs about $25 or $35. In Germany, the same service with synthetic oil is easily twice that much. A single quart of synthetic oil itself costs about 10 bucks.

TOM: The Europeans are trying to stretch the interval even farther. Manufacturers are reportedly trying to achieve a 30,000-mile oil-change interval with synthetic oil. So that might mean changing the oil once every three years over there!

RAY: Over here, we use mostly traditional, petroleum-based motor oil. And most manufacturers now recommend changing the oil every 7,500 miles. We recommend doing it every 5,000 miles, because we tend to be more cautious about protecting the engine. Very few people recommend changing the oil every 3,000 miles anymore. It's just not necessary, and the environmental cost is too high.

TOM: But maybe it's time for us to reconsider our recommendation? With engines AND oils getting better all the time, we might have to go up to 7,500 miles, too. Give us some time to think about it -- and dump our Exxon stock before making a formal recommendation.