The U.S. auto industry, starved for new-car sales, is pushing rebates and other buyer incentives to unprecedented lengths.

Ford Motor Co. yesterday announced it will provide two years of free routine maintenance and free repairs in most cases to customers who buy 1982-model Ford Escort and Mercury Lynx subcompacts between today and March 13.

"We're offering two years of virtually cost-free operation with the exception of gasoline and insurance," said Ford General Sales Manager Bernard L. Crumpton. The maintenance-and-repair offer does not cover damage due to accidents or driver abuse, nor to tires or lubricating fluids required between the normally scheduled maintenance overhauls.

In addition, Ford announced a 5 percent rebate on the base sticker price of 1982 Escort and Lynx models, worth between $250 and $400 depending on the price.

American Motors Corp. entered the competition Monday with an Old Car Retirement Plan, offering rebates of up to $500 to buyers who trade in their old cars of any make for 1981 or 1982 Spirits, Concord and Eagles.

AMC General Marketing Manager David Van Peursem said the top rebate of $500 will go to owners of 1974 or older models, with smaller amounts to those who trade in more recent models. Buyers also will receive the normal trade-in value for their used cars, he said. The rebate period ends March 31.

Last weekend, General Motors Corp. began a $4 million sweep-stakes campaign to promote its new models, offering 15 new GM cars to contest winners, plus other prizes. GM placed 41 million inserts in Sunday newspapers around the country, each containing a raffle number, with the prize numbers selected by computer. Dealers are posting winning numbers in showroom windows as well as entries in a second-chance drawing.

Chrysler Corp. has maintained rebates of from $300 on the subcompact Dodge Omni and Plymouth Horizon (except for the lowest-priced Miser models) up to $1,000 for the Chrysler Imperial and Dodge and Plymouth vans. Most truck models also are covered by rebate plans, which end Feb. 28.

Yesterday, Chrysler announced price increases for most subcompacts and compacts, ending a freeze begun in September that held prices of 1982 models at 1981 levels.

"Even with the price increases, our cars are priced equal to or below the competition," a Chrysler spokesman said. Wage concessions by union employes have given Chrysler a price advantage of between $200 and $500 a car over its U.S. competitors, according to industry analysts.

The increases varied from $230 for the Dodge Charter coupe, to $498 for the Dodge Aries and Plymouth Reliant front-wheel-drive, four-door compacts.

The Ford plan includes:

* Free scheduled maintenance for two years or 24,000 miles, which ever comes first, including all factory-recommended scheduled maintenance such as changing oil and filters. Parts and labor will be free.

* A two-year or 24,000 mile cost-free "workmanship assurance program" covering any defects or parts failure not due to accidents or driver abuse. Tires and auto fluids aren't covered (although oil changes during a regular maintenance overhaul would be free). The Fordcare plan will pay for replacement of parts that wear out in normal use such as brake linings and windshield wiper blades.

Ford will pay the entire cost of the program.