Motorists beware, the Environmental Protection Agency may be watching you.

For the past year EPA personnel have been staked out at gas pumps across the nation to see how many people are putting leaded gas in cars designed to take unleaded. The practice is known as fuel switching and it's illegal and the EPA wants to find out how bad it is.

Because there are almost 200,000 gas stations in the U.S. that are subject to the unleaded gas regulations the EPA has decided to hire a private contractor to do some of the work.

To help with the spying, EPA picked The Bionetics Corp., of Hampton, Va., a government support services contractor specializing in environmental monitoring. Bionetics will collect information on fuel switching in 12 states. But at Bionetics, they don't like to call it spying. Instead, it's known as "the observation of light-duty motor vehicle refuelings."

"These observations are strictly for data gathering purposes, not for prosecution," said an EPA spokesman. The civil penalty for a gas station operator convicted of fuel switching can range from $1,000 to a maximum of $10,000 per violation.

Using leaded gas in an unleaded car significantly increases the emission of lead, carbon monoxide and hydrocarbons into the air by gradually incapacitating the catalytic converter.

According to one EPA spolesman, the agency's fuel switching survey has shown that between 8 and 10 percent of all refuelings which should be with unleaded gasoline are in fact with leaded.

"We are trying to maintain track of how much fuel switching is going on and then factor that into policy decisions," said an EPA spokesman. EPA has long feuded with the Department of Energy over the extent of such fuel switching, claiming it is more widespread than DOE is willing to acknowledge.

There are basically two reasons why fuel switching is so tempting to motorists: leaded gas is generally cheaper than unleaded and it bgives better engine performance.

Last fall, the EPA began sending out teams of observers to some of the country's 200,000 gas stations. They picked the stations at random and placed their observers close to the pumps as possible without arousing suspicion.

Occasionally the gas station would have to be watched from a greater distance with the aid of binoculars.

The observers simply write down the license numbers of all the cars that pull up to the leaded pumps. Those numbers are then tun through the state motor vehicle administration to determine which of the cars requires a catalytic converter. The EPA is also keeping a record of how many retail gasoline operators are involved in fuel switching.

An EPA spokesman said that the agency plans to continue its nationwide observations and, depending, on budget considerations, may add more private contractors. He also said that EPA is considering using motorists from the agency to go directly into the stations and witness fuel switching first hand. CAPTION: Picture, no caption, By Bill Perkins - The Washington Post