In 2007, the Environmental Protection Agency will begin measuring not only exhaust emissions from diesel engines, but also emissions from the crankcase if it is not vented into the engine intake. The 2007 government standards for emissions of carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx) and particulate matter (PM) will also become more restrictive. There is the additional concern that crankcase emissions from present day trucks and buses may impact the quality of air inside the vehicle. This paper presents data to characterize crankcase emissions and examines a crankcase emissions abatement system (CEAS), the New Condensator®, manufactured by World NCI. Rather than allowing crankcase emissions to leave via a vent tube, a CEAS re-circulates the emissions to the intake of the engine.In this study, crankcase and tailpipe emissions were measured from a 1996 Peterbilt tractor truck powered by a Caterpillar 3406, 550hp engine with approximately 400,000 accumulated miles, to quantify the emissions benefits of closing the crankcase with the CEAS. Emissions were measured while the vehicle was exercised through the Urban Dynamometer Driving Schedule (UDDS) at a test weight of 56,000 lbs. Crankcase emissions were directed to a dilution system for measurement of regulated species. The total diluted crankcase flow was passed through filters which served to measure total crankcase PM and the filters were subsequently analyzed for hopanes and stearanes as markers for lubricating oil to determine the source of the collected PM. From the overall analysis, crankcase total PM was the highest species relative to tailpipe emissions at 5.66%. Crankcase HC, CO and NOx were 3.68%, 1.25% and 0.09% of the tailpipe emissions, respectively. The tailpipe emissions were also measured after closing the crankcase with the installation of the CEAS. Then, to condition the CEAS, the tractor was operated for a total of 13,400 miles with the CEAS installed. After this mileage accumulation, the tailpipe emissions were again measured on the chassis dynamometer with and without the CEAS installed.In addition to measuring PM mass, the researchers characterized the size distribution of the dilute crankcase PM with a Cambustion DMS 500. The total particle number concentrations were in the order of 107 per cm3, and the mean size of the particles was approximately 70nm.