Dear Car Talk:

We just bought a brand-new Subaru Crosstrek. The dealer says it uses synthetic oil and that the oil changes will cost $75. Do we have to use synthetic oil? Is $75 a reasonable price? Sounds like a lot when we're used to paying $35 for an oil change.

-- Sherri

Congratulations on your brand-new heap, Sherri! I like the Crosstrek.

It does use synthetic oil. In my experience at the garage, synthetic oil is superior to standard motor oil, and it makes sense that more and more manufacturers require it now.

It does seem to provide superior lubrication. Not only is it more "slippery" than conventional oil, but it lubricates better in both very cold and very hot temperatures, which reduces wear and makes the engine last longer.

The other great advantage of synthetic oil is that it maintains its lubricity longer than regular oil. So instead of doing an oil change every 3,750 miles, you can do it every 7,500 miles, for instance. Some manufacturers go even longer.

So the math works out about the same. You pay twice as much for your oil changes, but you do them only about half as often. And, presumably, you'll save money on engine repairs later in the car's life. And you might even get a little better mileage with the synthetic.

And because you're draining out old oil less often, you're creating less waste oil, which is better for the environment. And $75 is not an unreasonable price for an oil-and-filter change with synthetic oil. You might be able to do a little bit better at an independent shop, but the dealer is not taking advantage of you, Sherri.