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Sludge and Varnish Evaluation of Polyether Amine Gasoline Fuel Additives at “Complete Fuel System Cleaner” Aftermarket Fuel Additive Concentrations
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on September 15, 2020 by SAE International in United States
Sludge and Varnish deposits that can build up in the crankcase originate in large part from fuel and fuel components that enter the crankcase through blow-by. These deposits can lead to a variety of engine issues including piston skirt deposits, cylinder bore scuffing, stuck lifters and oil filter plugging. A test has been developed to evaluate the contribution of “Complete Fuel System Cleaner” (CFSC) aftermarket fuel additives to crankcase sludge and varnish deposit formation. CFSC aftermarket fuel additives are typically formulated with polyether amine (PEA) chemistry and at concentrations that exceed 2000ppm. Three different commercially-available CFSC products were tested, containing two different classes of PEA chemistry - propylene oxide-based PEA (“PO-PEA”) and butylene oxide-based PEA (“BO-PEA”). Two of the three products contained the same PO-PEA chemistry, but at different concentrations, to show the effect of additive dosage. Using the Sequence VG sludge and varnish test rating criteria, it has been shown that PO-PEA can lead to a borderline failing result for varnish formation at the lower treat rate, and an extreme failing result at the higher treat rate. BO-PEA chemistry did not lead to noticeable varnish formation. All three of the tested additives yielded passing sludge formation results, though a slight degradation in sludge control was observed with PO-PEA at the higher concentration. Analysis of the used test oil demonstrated that the BO-PEA chemistry led to a 73% improvement in oxidative stability, when compared to used oil from PO-PEA testing. It is hypothesized that the lower solubility of PO-PEA can contribute to the formation of sludge and varnish precursors that have the potential to cause significant engine harm.