INDIANAPOLIS, IN -- How much would you pay never to change your oil again?

Wait, don't answer yet. With this offer, we'll throw in a reduced environmental impact and lower oil consumption. It's not sold in stores, but the technology is here, and it may be less than you think.

U.K.-based T&N plc, a specialist in engine components and bearings, says it expects a major European carmaker to begin installing its centrifugal filtration system as original equipment on a gasoline engine-equipped passenger car by 1997.

The T&N system provides the vehicle with a fit-for-life filter that eliminates the need to change the oil and filter and reduces long-term wear on the engine.

The centrifuge spins out all particles that are denser than oil, effectively removing particles down to less than five microns.

Mark Backhouse, business manager for Glacier Filter Products, part of the T&N bearings group, says these small, often extremely hard particles provide a significant source of long-term wear on an engine. "The paper filters are rated at 15 to 20 microns, and they take out the large stuff. But the smaller ones get through so the engine wears. With the centrifuge the engine actually runs longer because the smallest particles are taken out." The engine functions more efficiently over its life, reducing total emissions as well, Mr. Backhouse adds.

The centrifuge is a bypass system processing 15% of the total oil volume at any time. It is complimented with a full-flow metal screen that is installed where the traditional paper filter was fitted. This provides a catch for particles 50 microns or greater in the system to prevent any large debris from seizing the engine. The metal filter never needs to be changed because of the infrequent presence of these large particles. "Statistically, we found that an engine has only one large particle in a million particles, so the full flow wire filter will not clog," says Mr. Backhouse.

The centrifuge unit houses a central spindle and a central spinning rotor. Oil at pump pressure passes through two tangentially opposed nozzles into the system, causing the rotor to spin. The resulting centrifugal force, reaching up to 3,000 g, forces all particles with a density higher than oil to move to the circumference where it forms a dense, dry particle cake.

T&N and major OEMs have conducted tests indicating that the filter system works sufficiently over 60,000 miles (100,000 km). Those same test cars are now achieving 100,000-mile (160,000-km) distances without the need for an oil change.

"We had mechanics break apart the engine at 60,000 miles without knowing where the engine came from or how long it had been driven. They were rating these engines as having only 20,000 miles of wear. And these guys look at engines every day," says Mr. Backhouse. "Then we reassembled them, and these engines have passed the 160,000-km (100,000-mile) mark."

The centrifuge system is composed of aluminum and steel. Cost to the OEM is between $20 and $25. The filters will be assembled in the U.K. until demand increases enough to shift production to other facilities around the world. Initial volume is expected to be around 50,000 units in the first year. T&N won't disclose the OEM, but indicated that the automaker is a high-volume European passenger-car manufacturer, and that the centrifuge will land on a 2L to 2.5L engine.

Centrifuges have been used on heavyduty diesel engines to remove particles and soot for several decades. The recent extension of the technology into the passenger-car market is likely to impact the oil and paper filter industry. Eliminating oil changes would significantly reduce the amount of disposed paper filters that are often discarded in landfills or incinerated. In the case of landfill disposal, often the excess oil leeches into the water table, contaminating municipal systems that supply the drinking water. T&N estimates that between 1.5 and 2 million paper filters are changed every day in the U.S.

The resulting cake from the rotor is still waste material that must be disposed either in landfill or through incineration. But the total waste volume is significantly smaller than the mass resulting from repeated filter and oil disposal.

"At some point, someone has to face up to this problem. Here we are going into the year 2000 and we are still dumping dirty oil filters and oil all over the world," says Mr. Backhouse. "In the U.K., we're a lot smaller than America. We have nowhere to dump it." Oil consumed during the life of a car also will drop dramatically. During the life of a 100,000-mile engine, 30 or more 4-quart oil changes are necessary, or 3/4 of a barrel of oil.

Paper filter manufacturers generally contend that particles less than 20 microns are not a factor in engine wear. "They would probably say that it isn't the small particles that hurt an engine, it is the larger ones. But anyone that knows bearings knows that isn't true -- and we know bearings," says Mr. Backhouse.

Service costs also will be reduced for car owners. Automakers have been searching for a maintenance-free 100,000-mile engine, and although General Motors Corp.'s Northstar V-8 and Ford Motor Co.'s Duratec V-6 do not require tuneups, oil still needs to be changed. T&N's centrifuge technology appears to offer OEMs the final element in the 100,000-mile, maintenance-free engine.

T&N's filter technology has some mild criticism. "Seventy percent of oil is additives. What happens to the viscosity modifiers, the detergents and dispersements?" asks Chuck Smith, manager of field services for Purolator Products Inc., one of the largest suppliers of paper filters. "You have chemical reactions that take place in the oil, so the additive package starts to change over time." Mr. Smith also notes that the system is still a bypass filter, and the screen does not provide an adequate full-flow stop for medium-size particles. "If you have a volume of oil with known contaminants, and you pass it through 15% at a time while the other 85% goes through a 50-micron screen, anything less than 50 microns in that 85% volume is going to zip right through. Putting this system on a gasoline engine and not using a full-flow filter -- I would be very skeptical," he says.

T&N says that the centrifuge's durability is demonstrated by the heavy-duty vehicle applications on Renault SA and Mack Trucks Inc. Class 7 and 8 vehicles, along with other heavy-duty truck OEMs. "We've been putting these into heavy trucks for 25 years. They go all over Africa and Scandinavia. They perform extremely well under these severe circumstances," says Mr. Backhouse. T&N currently supplies 40 engine manufacturers including marine, industrial and generator as well as transportation applications. Current production volume is 200,000 units annually. T&N says that 96% of the centrifuges produced in the U.K. are exported.