DETROIT - Dollar Thrifty Automotive Group Inc said on Monday it would cut back sharply on 2010 car rental purchases from Chrysler and that its average fleet costs had stabilized at levels it hoped to maintain next year.

Chrysler, which had made up 76 percent of Dollar Thrifty's total U.S. fleet purchases in 2008, will make up about 30 percent of 2010 fleet purchases, said the company, which rents under the Dollar Rent A Car and Thrifty Car Rental brands.

Ford Motor Co will make up 34 percent of its purchases and General Motors Co another 20 percent, Dollar Thrifty said. The rental car company executed a three-year deal with Ford in February.

Nissan Motor Co Ltd will make up 6 percent of its fleet purchases. The rest will come from Hyundai Motor Co and Kia Motors Corp of Korea, and other automakers.

The car rental group had an agreement with Chrysler that required it to buy 75 percent of its fleet from the automaker, which restructured in a government-supported bankruptcy and is under management control of Italy's Fiat SpA.

Dollar Thrifty and Chrysler reached a new deal in August that replaced the percentage minimum with a requirement for a fixed volume of vehicle purchases per program year.

Dollar Thrifty said it had substantially completed its 2010 model year ordering plan and the more diverse lineup would spread out its potential risks from changes in vehicle residual values and automaker vehicle production plans.

The company also said it now expects fleet costs to be below $350 per unit per month in the third and fourth quarters and to remain stable below that level in 2010. Previously it had expected to meet that level some time in 2010.

Fleet depreciation costs per vehicle improved during the third quarter from the second quarter due to improving residual values both from the strengthening in the used car market and improved economics on its 2010 purchases, Dollar Thrifty said.

Shares of Dollar Thrifty rose 2 cents, or 0.08 percent, to $26.20 on the New York Stock Exchange at mid-afternoon.

(Reporting by David Bailey; Editing by Richard Chang)