In modern diesel engines, acidity generally determines the lubricant drain interval. To control acidity, lubricant suppliers incorporate detergent additives to neutralize acids that accumulate in the oil via exhaust blow-by and base-stock oxidation. However, formulations that meet the most recent diesel lubricant classification specifications typically contain lower levels of detergent since this additive contributes to ash that fouls emissions aftertreatment systems. This study explores a novel approach to lubricant acid control as a potential means to reduce additive requirements or increase oil drain interval. The authors investigate the performance of an innovative oil filter that releases no additives into the lubricant, yet enhances the acid control function typically performed by detergent and dispersant additives. The filter chemically conditions the crankcase oil during engine operation by sequestering acidic compounds derived from engine combustion and lubricant degradation. Long duration heavy-duty diesel engine tests show that the filter reduces both the rate of Total Base Number (TBN) decline and the rate of Total Acid Number (TAN) increase by a factor of two. Analysis by Fourier transform infra-red (FTIR) spectroscopy also indicates that lubricant oxidation may be lowered. In addition, these results suggest a reduction in engine wear. These results imply that lower lubricant additive levels in combination with this novel oil filter may be used to reduce ash accumulation in diesel aftertreatment systems, while maintaining adequate engine protection. The results also indicate that the engine operator may use this oil filter with a state-of-the art lubricant to lengthen oil change intervals.

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