An Experimental Evaluation of the Impact of Lubricating Oils and Fuels on Diesel Particulate Filters

A previous experimental work had been carried out in our laboratories to investigate the impact of lubricating oil formulations on deposit accumulation of a continuously regenerating Diesel Particulate Filter. Tests on a passenger car diesel engine were conducted with the use of an accelerated test procedure aimed at enhancing the oil effect on filter weight increase and exhaust gas backpressure.

The accelerated test procedure [1], which had proved to be a good tool to discriminate in short time oils having a different impact on DPF performances, was here used to evaluate the behavior of two different types of DPF systems, using oils characterized by different ash content. A slight difference emerged from the comparison between DPF types in terms of accumulated deposits as a function of oil sulfated ash. An experimental section was dedicated to the evaluation of the impact of oils and fuels characterized by different sulfur content. Moving from a low S product to a high S one, a marginal effect on DPF ash deposit accumulation emerged, while a higher impact on exhaust backpressure along the test occurred.

Further tests pointed out that a fuel having significant presence of ash forming compounds leads to a high fuel contribution to DPF non-regenerable deposits. The use of both standard and non-standard fuel filters did not give significant variations. These results point out the importance of gaining more knowledge on the contribution of a possibly contaminated fuel to DPF weight increase and achieving a greater understanding of the role of fuel filters in limiting fuel contribution.

DPFs were subjected to a post mortem analysis to characterize the accumulated deposits with the use of different analytical methods (XRD, SEM/EDX) .