But with gas prices topping $3, being known as the flagship of fuel economy creates its own demand. Toyota ended May with a nine days' supply of Priuses on hand — most Toyotas average about 30 days' supply — and Morgan Stanley analysts calculated that at the May rate of sales, Toyota could move 244,000 Priuses a year.

The booming sales of the Prius may also be due to the lack of a head-to-head comparison with other Toyota vehicles. A buyer considering other hybrids, such as the Toyota Camry sedan and Ford Escape SUV, can usually stroll across a dealer's showroom and see a non-hybrid model of the same vehicle for $3,000 to $5,000 less before any incentives, a gap that isn't always overcome by the hybrid's fuel savings.

"You can't help but see how much less you'd be paying for what looks like the identical vehicle, and it invites comparison," Libby said. "Long term, the premiums should decline, and it should be less of an issue."

Even excluding the Prius, Toyota's other hybrid models combined to outsell the rest of the industry, with its Camry hybrid racking up 6,853 sales and its Highlander Hybrid SUV selling 3,312.

Some analysts said Toyota's hybrid models may reinforce the company's image even if their sales are relatively limited. Art Spinella, an industry analyst with CNW Marketing/Research, said a recent survey of 5,400 car shoppers showed buyers placing Toyota second only to Honda Motor Co. for leading the industry with environmental technologies, a position Toyota would not have held five years ago.

"Being green is reaching critical mass proportions," Spinella said.

Hybrid sales also increased at other automakers. Honda sold 4,520 Civic hybrids, a 50 percent increase from a year earlier. Ford's sales of the hybrid Ford Escape and Mercury Mariner SUV hit a monthly record of 3,214 in May. General Motors Corp., which offers a hybrid Saturn Vue SUV and Saturn Aura sedan, does not release separate hybrid sales figures.

George Pipas, Ford's director of industry sales analysis, said the automaker plans to sell about 20,000 hybrids this year, same as the previous year, but faced a challenge in getting buyers to give its more efficient models a chance.

"Consumers think about us in truck and SUV terms," said Pipas. Toyota's "reputation for fuel efficiency is a big plus for them, where we have to communicate it and raise awareness."

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© 2007, Detroit Free Press. Distributed by McClatchy-Tribune Information Services.