A 2007 Cummins ISL 8.9L direct-injection common rail diesel engine rated at 272 kW (365 hp) was used to load the filter to 2.2 g/L and passively oxidize particulate matter (PM) within a 2007 OEM aftertreatment system consisting of a diesel oxidation catalyst (DOC) and catalyzed particulate filter (CPF). Having a better understanding of the passive NO₂ oxidation kinetics of PM within the CPF allows for reducing the frequency of active regenerations (hydrocarbon injection) and the associated fuel penalties. Being able to model the passive oxidation of accumulated PM in the CPF is critical to creating accurate state estimation strategies. The MTU 1-D CPF model will be used to simulate data collected from this study to examine differences in the PM oxidation kinetics when soy methyl ester (SME) biodiesel is used as the source of fuel for the engine.A test procedure developed by Hutton et al., was modified to improve the ability to model the experimental data and provide additional insight into passive oxidized PM in a CPF. A test protocol and plan was developed to allow PM oxidation rates by NO₂ to be determined from engine test cell data. An experimental matrix consisting of CPF inlet temperatures from 250 to 450°C with varying NOX/PM from 25 to 583 and NO₂/PM ratios from 5 to 240 was used.SME biodiesel was volumetrically blended with ULSD in 10% (B10) and 20% (B20) portions. This blended fuel was then used to evaluate the effect of biodiesel on passive oxidation rates. Four tests were performed with B10 and four tests with B20. Gathering data to determine the effect of fuel type (ULSD and biodiesel blends) on PM oxidation is the primary goal. Data from fifteen tests completed with ultra-low sulfur diesel (ULSD) fuel and one additional engine platform is used to compare to results from SME biodiesel tests.The experimental reaction rates during passive oxidation varied based upon the average CPF temperature, NO₂ concentrations, and the NOX/PM ratios for each engine and with all fuels. The data collected is directly comparable to ULSD data from prior experimental tests, but requires a high fidelity model that includes NO₂ and thermal oxidation mechanisms and back diffusion to determine the details of the PM oxidation process.