Rig and Engine Tests Demonstrate Improved LNT Durability and Low-Temperature Performance with Newly Developed Particles: Diesel combustion improvements for reducing exhaust emissions and fuel consumption generally decrease exhaust gas temperature. This trend of decreasing exhaust gas temperature is not desirable for the lean NOx trap (LNT) to reduce NOx emissions to ultimately low levels at the tailpipe. The sulfur contained in both fuel and engine oil forms sulfates on the catalysts and prevents the LNT from adsorbing NOx from exhaust gas. Generally, catalyst temperature increases to about 1,000 deg.K to restore catalyst performance; however, repeatedly exposing the catalyst to such a high-temperature environment causes catalyst performance to deteriorate due to the sintering of the substrate material. Typically diesel fuel is injected into exhaust gas upstream from the LNT to enrich the environment and to produce such reducing agents as the HC and CO required for the LNT to reduce NOx. Low LNT performance requires an increase in the amount of diesel fuel injection which is not desirable from the fuel economy standpoint. A group of researchers from Mazda Motor Corporation, Toda Industries, and Ohita University developed a substrate material of small particles to reduce sintering. This chapter reports test results obtained on a test rig and a test engine and the characteristics of the hollow particles obtained through various laboratory analyses. The chapter consists of 9 pages including 13 figures.