"Your mileage may vary." Yes, indeed—it could be as much as 30 percent lower than government ratings, as some new owners of hybrid-electric vehicles discovered, to their dismay, last year.

If 2004 began with drivers in the United States and a few other places giving hybrids a heartfelt hug, it ended with a more subdued embrace. One of the reasons was disappointment over real-world mileage. Official ratings for fuel use, based on the outdated driving patterns of U.S. government tests, turned out to be a poor predictor for what typical buyers could expect.

But if the hybrid honeymoon is over, the marriage is still in solid shape. In some areas, a buyer must wait months for a Toyota Prius. Toyota plans to build 100 000 Priuses in 2005, up from 67 000 last year. Waiting in the wings is the Lexus RH 400h luxury hybrid sport utility vehicle, now scheduled to go on sale 15 April in the United States. As of December 2004, buyers had already paid deposits for half of the year's production of 20 000.

Hybrids are now also offered or planned by Ford, General Motors, Honda, Nissan, and Toyota. GM and DaimlerChrysler announced that they would get together to develop a full-hybrid system to be offered in the 2008 model year. Even Porsche confirmed that it might license Toyota's hybrid technology for its sport utility Cayenne, infuriating die-hard fans of the company's signature lithe, high-performance sports cars.

Still, though hybrids are hot, no single vehicle is likely to make as much of a splash this year as the revamped Prius did in 2004. The closest thing to a recurring theme in 2005 will be electronic stability control. It will shift from an expensive option to a necessity on the tall, heavy sport utility vehicles that still make up one of the most popular categories in the United States. Daimler, Ford, and GM announced that stability control would be standard on all their SUVs by the 2007 model year. The notice followed the release of a study by the U.S. National Highway Traffic Safety Administration that found stability-control technology reduced single-vehicle crashes in SUVs by 67 percent and fatal crashes by 64 percent.

Among concept cars, hybrid electrics are still going strong, and more of them are being built with lithium-ion batteries rather than the standard nickel-metal hydride. Lithium-ion, now used mostly in consumer electronics, offers close to twice the energy density of nickel-metal hydride. The wildest lithium-ion vehicle so far has to be the luxury-sedan concept Eliica from Keio University in Japan, reminiscent of nothing so much as the nuclear-powered, six-wheeled pink Rolls-Royce that ferried Lady Penelope Creighton-Ward in the 1960s children's TV puppet show "Thunderbirds." Built by a team from the Electrical Vehicle Laboratory at Keio University's Faculty of Environmental Information, the Eliica has eight wheels and a projected top speed in excess of 368 km/h (229 mph). Unlike Lady Penelope's car, it will not be offered with a machine gun that deploys from the front grille.

Elicia Eight wheels, eight motors, no tailpipe

Aficionados know that every auto show has its share of malproportioned design exercises, technical oddities, and just plain weirdness. But to make jaws drop in awe at an international auto show—that takes some doing.