General Motors is fighting back against high petrol prices in the United States with an unusual sales incentive dubbed the 'GM Fuel Price Protection Programme' for some of its 2006 and 2007 GM full-size utilities and mid-size cars.

This regional programme - limited to the 'sunshine' states of Florida and California - caps what consumers pay for petrol at $US1.99 a gallon (it's currently averaging just under $3 nationwide), according to GM.

As ever with such promotions, 'terms and conditions apply'. The main one is that vehicle buyers must sign up (and pay a monthly fee) for GM's OnStar telematics service.

"This programme gives consumers an opportunity to experience the highly fuel-efficient vehicles GM has to offer in the mid-size segment," said GM southeast regional general manager Dave Borchelt in a statement.

"It helps protect consumers against rising fuel prices by providing them with a partial credit for their fuel purchases for one year."

"This incentive is likely to get the attention of many consumers," said executive director of industry analysis.

"The psychological impact is immeasurable; the actual dollar savings amounts to about $1000 per vehicle."

GM said the credit is based on the consumer's estimated fuel usage each month. Fuel consumption is calculated based on the mileage driven, as recorded by OnStar and the EPA city fuel economy mileage rating for the vehicle.

Using the calculation of the consumer's estimated fuel usage each month, they will be credited for the difference between the average price per gallon of premium fuel in their state, as published by the Automobile Association of America (AAA), and the $1.99 petrol price protection cap.

The credit will be applied each month to a pre-paid card, which will be issued to the consumer. The credits are good until 31 December, 2007 and may be used for any type of purchase at any location that accepts MasterCard. There is no mileage limitation.

According to GM, a California resident who purchases a 2007 Chevrolet Tahoe and drives it 1,000 miles (1,600km) a month, would realize an estimated $103.75 monthly credit, based on the 15 May average premium fuel price of $3.65/gallon. A Florida resident who purchases a 2006 Buick LaCrosse with the standard V6 engine and drives about 1,000 miles a month, would see an estimated monthly credit of $60, based on the current average premium fuel price of $3.19/gallon in that state.

Buyers will also be able to go to a web site to calculate their potential savings based on their vehicle selection.

To participate in the programme, consumers who reside in California and Florida must purchase or lease and take delivery of an eligible vehicle between 25 May 25  and 5 July 5, 2006 and enroll in the OnStar Vehicle Diagnostics service.

Eligible vehicles in California include 2006 and 2007 Chevrolet Tahoe and Suburban (one-half ton models only), Impala and Monte Carlo; GMC Yukon and Yukon XL (one-half ton models only); Hummer H2 and H3; Cadillac SRX; Pontiac Grand Prix; and Buick Lucerne.

Eligible vehicles in Florida include the 2006 and 2007 Chevrolet Impala and Monte Carlo, Pontiac Grand Prix and Buick LaCrosse.

GM said the selected vehicles "were chosen because of their outstanding fuel economy and great consumer appeal".