Unleaded gasoline was used in a 30 car, 48,000 mile taxicab field test to study the effects of a deposit control (DC) gasoline additive and lubricating oil additives on engine deposits, wear, and other variables. The unleaded gasoline performed as well as or better than a leaded gasoline in this test when both gasolines contained the DC additive. Engine deposits were comparable, and wear and corrosion were reduced when unleaded gasoline was used.
With unleaded gasoline, we found motor oils need a high level of ashless dispersant to obtain maximum varnish control. Also, in these test engines, an ashless oil gave the same wear protection with unleaded gasoline that an SE-type oil gave with leaded gasoline.
A highly effective DC gasoline additive minimized carburetor, intake valve, and crankcase deposits with unleaded gasoline. This agreed with the effective performance that this additive had previously shown in leaded gasoline service. Also, unleaded fuel with the DC additive used with a nondispersant crankcase oil performed similarly to a nonadditive unleaded fuel used with an SE-type oil in the control of engine sludge and varnish.