The panel says that the EPA settlement will have no impact at all on an urban-type vehicle, since the engines were designed to meet EPA tests of in-city driving. The manufacturers have had to change the electronics for over-the-highway engines, but say there will be no noticeable impact in fuel economy or performance.
However, there is some potential impact on oil contamination and oil drain intervals. The retarded timing needed to cut the oxides of nitrogen emissions means there will not be full combustion. Some of the unburned fuel will make its way into the oil as soot. The panelists recommended using the premium API CH-4 oils, which were designed to handle higher levels of soot.
The higher levels of soot also may mean that fleets that have been extending their oil intervals may find they have to go back to shorter intervals. The additional soot in the oil could form deposits in the engine, which will severely affect engine life.
For the next big emissions cut in 2002, manufacturers are looking at new technologies for truck engines.
The starting point will be exhaust gas recirculation, or EGR, which has been used for years in passenger cars. The major difference in heavy truck engines is that the exhaust gases will have to be cooled before they are blended into the air stream coming into the turbocharger. This will mean an increased load on the cooling system.
The second alternative they’re studying seriously is exhaust aftertreatment – similar to the catalytic converters found on cars and light trucks. One way to do this on heavy trucks is to use a chemical, actually a fertilizer, called urea. When injected into the exhaust, it turns to ammonia and burns off NOx. However, this would mean adding another small tank on the truck – and there aren’t exactly an abundance of urea pumps at your favorite truckstop.