A car's computers can tell you everything, such as how tightly your gas cap is fitting, what your fuel efficiency is and even what your wheel speed is to control the brakes.



Now this new technology has an added bonus: It's part of the reason behind the easing up and eventually phasing out of the state's emission-testing law. Owners of newer cars will be exempted from the state Department of Ecology's testing program under new rules, adopted this week, that will go into effect in July 2012.



All 2009 and newer cars won't have to undergo emission tests, and additional businesses, such as car dealerships, may be authorized to do the tests. The new rules eliminate some testing that is believed less relevant as vehicles become more fuel-efficient.



The state now tests about 1 million cars a year, said John Raymond, a planner with the air-quality program with the Department of Ecology. The state already exempts from testing cars that are five years old or newer, so the new law won't really go into effect until 2014.



That year the state expects to test just 88 percent of the state's vehicles, or 880,000.



By 2019, when the program is scheduled to end, just 54 percent of the vehicles, or 544,000, will be tested.



The state first began testing cars in 1981. But the state Legislature has not authorized a vehicle-emission program beyond 2019 because cars are expected to be clean enough by then that air quality won't be a problem, Raymond said.



The changes are expected to save car owners and testing facilities about $19 million, according to the ecology department.



Of the current $15 testing fee, $12 goes to the contracting agency that runs the station and $3 into the state's general fund, or about $3 million a year.



Among the other rule changes:



• The state will no longer require testing of a vehicle's gas cap. Raymond said the car's computers will check on this and the testing is no longer required. That will save $2.5 million in equipment and staffing.



• People will be able to have their cars tested at a private testing station, such as an auto dealership, where there's no limit on what they can charge. Raymond said some owners may find it more convenient to have their car tested at a dealership and save a trip to an emission-testing station — even if it costs more money. That change is expected to save $8.5 million because the state expects maybe 10 percent of vehicle owners will opt for a private testing site. But it's also not clear whether the dealerships will want to invest in the expensive equipment needed to do the testing.



• Light-duty diesel trucks won't have to go through emission testing because they aren't big polluters.



Raymond said less than 10 percent of vehicle owners fail the emissions test. If they do fail and spend at least $150 to try to get their cars to pass and still fail, the vehicle owner can get the emission test waived for that test cycle. Cars must go through emission testing every two years.



The state doesn't plan to add more emission stations but may expand the hours at existing ones for convenience.



Only vehicles in King, Pierce, Snohomish, Clark and Spokane counties, the state's most-populous counties, are required to go through emission testing.