Great hotel deals not written in the stars.(up front: News / Trends / Advice)(General Motors Hummer H3)

Anyone who has booked a hotel room after checking with the American Automobile Association, Mobil Travel Guides, or an online site is familiar with the one-to-five rating system. The more diamonds, stars, or smiley faces (for Travelocity's customer reviews), the better the hotel--supposedly

But we found that you can't always count on the stars to guide you. There are almost as many rating systems as raters, and they sometimes disagree. That can lead to letdowns once you've checked in.

We compared the marks that seven rating groups gave three dozen hotels in Orlando, Fla., and Las Vegas, two of the most frequently visited U.S. destinations. The groups were AAA and Mobil plus leading travel Web sites Expedia, Hotwire, Orbitz, Priceline, and Travelocity

No hotel in our sample earned the same rating across the board. Most were ranked within one star of one another, but The Venetian in Las Vegas earned three stars from Mobil, four diamonds from AAA, and five stars from Orbitz.

Priceline says that Hotwire frequently inflates its ratings to make its deals appealing, but no site we studied was consistently higher than others in scoring our hotels. We did find that Mobil--whose inspectors assess cleanliness, amenities, and service--gave the lowest ratings. "There are a lot of four-star facilities out there, but without four-star service they'll get rated a three-star," says Shane O'Flaherty, Mobil Travel Guide's vice president for quality assurance.

AAA's system is similar to Mobil's. "We have 65 inspectors out there full-time looking under beds and by the toilets," says Michael Petrone, AAA's director of tourism information development. But AAA weights the criteria differently.

The Web sites typically include marks from AAA and Mobil, but they mix in lists of amenities and customer feedback. And their definitions of the rating levels, published on the sites themselves, can differ. The Travelocity site, where you'll find AAA's diamonds in addition to the site's own stars and smiley faces, actually says, "The display of AAA Diamond ratings on this site is not meant in any manner whatsoever to suggest equivalence to Star ratings. Any similarity between the two rating systems is purely coincidental."