(FORTUNE Small Business) – In its Annual Car Issue, published last month, Consumer Reports stunned the auto world by ranking European luxury cars from Mercedes, BMW, and Jaguar among the worst for reliability, behind models from domestic automakers. That's never happened in the history of the rankings. If you're shopping for a car, Consumer Reports is a good place to start, in part because it isn't afraid to publish controversial results. (Its parent company goes to court later this year to defend a 1988 review saying that the now discontinued Suzuki Samurai could tip in sharp turns.)

The catch is that sometimes the rankings seem contradictory. For instance, Consumer Reports gives the Volvo XC90 its highest rating for owner satisfaction, indicating that 80% or more of XC90 drivers would buy another. But that model also gets the lowest rating for predicted reliability, because of problems during the first year of production. Conversely, the Mitsubishi Montero Sport gets the highest rating for reliability and the lowest for owner satisfaction. What's going on here?

Most surveys measure one of two attributes: quality (how many problems a car has--both right out of the show room and after a few years of wear and tear) and satisfaction (how happy the customer is with the car). Problem is, the two measures sometimes don't point in the same direction. Consumer Reports, which surveys 600,000 subscribers to compile its rankings, says there is "almost no" correlation between owner satisfaction and predicted reliability. Why? Some well-made, plain-vanilla cars and minivans may seldom break down, but they're also less likely to peg the excitement meter than a slick, if unreliable, sports car or SUV.

After Consumer Reports, the most influential rater is J.D. Power & Associates, a for-profit marketing firm that has been measuring consumer opinions since 1968. J.D. Power publishes four key surveys on vehicle quality and customer satisfaction. And for those who want to get their fingers dirty in the data, Edmunds.com, an online new- and used-car price guide, publishes depreciation ratings from the definitive Automotive Lease Guide, along with thousands of verbatim comments from customers.

With a little experience, you can learn to read between the lines. Take BMW's wildly popular Mini Cooper. The car scores high with Edmunds's customers but lower with Edmunds's editors. It has more than twice as many problems as the top-ranked car in J.D. Power's Initial Quality Study. Consumer Reports ranks it at the top in owner satisfaction and at the bottom in predicted reliability. Translation: If you're more interested in sizzle than steak, this is the car for you.

As for me, I'd note that Toyota and Honda hold down 40% of the spots on CR's list of "good bets"--cars that have had better than average reliability for a number of years. And one car that perennially scores at or near the top of almost every survey is Lexus's flagship sedan, the LS 430.