DETROIT -- General Motors will help foot the high cost of gasoline for auto shoppers in California and Florida.

GM is starting a marketing program in those two states that caps gasoline prices at $1.99 a gallon when a consumer buys a certain GM vehicle.

"Fuel prices are very high in those states, and both are key markets for us where we want to increase our market share," says Jeff Kuhlman, a GM spokesman.

The plan is called GM Fuel Price Protection Program and starts Thursday, May 25.

Here's how it works:

A consumer who buys or leases a certain GM vehicle between May 25 and July 5 will get a guaranteed gasoline rate of $1.99 a gallon for 12 months.

GM will pay the difference between $1.99 and the average price of premium gasoline as calculated by AAA. Buyers can drive an unlimited number of miles, which are tracked by OnStar.

$104 monthly savings

For example, a California resident who buys or leases a 2007 Chevrolet Tahoe SUV and drives it 1,000 miles a month would see a monthly savings of about $103.75 based on the current California average premium gasoline price of $3.65 a gallon, GM says.

A Florida resident who buys a 2006 Buick LaCrosse sedan with the standard V-6 engine and drives about 1,000 miles a month would see a monthly savings of about $60 based on the current Florida average premium gasoline price of $3.19 a gallon.

The credit will be applied each month to a prepaid card, which will be issued to the consumer. Those are good until Dec. 31, 2007, and can be used for any type of purchase on MasterCard.

The LaCrosse buyer in GM's example would receive $720, less than a typical cash rebate. Consumers may receive any other purchase incentives offered by the automaker.

In California, the selected vehicles include 2006 and 2007 models of the Chevrolet Tahoe and Suburban, GMC Yukon and Yukon XL, and Hummer H2 and H3 SUVs; Chevrolet Impala, Chevrolet Monte Carlo and Pontiac Grand Prix, and Buick Lucerne sedans; and the Cadillac SRX crossover.

In Florida, the eligible vehicles are 2006 and 2007 models of the Impala, Monte Carlo, Grand Prix and the Buick LaCrosse sedan.

If the program is a hit, GM will consider expanding it to other areas.

Strong sales

GM's nationwide sales for the mid-sized cars included in this program are up 20.4 percent through April compared with the year-ago period to 190,151. That boost is largely due to the strong sales of the Lucerne, Impala and Grand Prix.

GM's sales for SUVs and the SRX are also up 18.3 percent through April, boosted by strong Hummer H3 and Tahoe sales.

Sales of the redesigned 2007 Tahoe are up by 35.5 percent in that same period. The Hummer H2 sales fell 24.2 percent through April compared with the year-ago period to 5,717 units, but the new H3 smaller SUV has sold 16,582 units through April.

GM plans to start marketing the fuel price program through direct mail, TV, radio and print advertising in those two states, Kuhlman says.

Starting Friday, May 25, consumers can go to www.fuelprotection.com to calculate potential savings on a selected vehicle.