TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Additive: The nitrogen-containing detergent additive is aliphatic hydrocarbyl amines, hydrocarbyl poly(oxyalkylene) amines of formula (I), hydrocarbyl-substituted succinimides, Mannich reaction products, nitro and amino aromatic esters of polyalkylphenoxyalkanols, and/or polyalkylphenoxyaminoalkanes.Preferred Amine: The aliphatic hydrocarbyl amine is polyisobutenyl or polyisobutyl monoamine or polyamine. The hydrocarbyl poly(oxyalkylene) amine is hydrocarbyl poly(oxyalkylene) monoamines or polyamines, where hydrocarbyl group contains 1-30C, the number of oxyalkylene units is 5-100, and the amine moiety is derived from ammonia, a primary alkyl or secondary dialkyl monoamine, or a polyamine having a terminal amino nitrogen atom. It is preferably an alkylphenyl poly(oxyalkylene) monoamine, where the poly(oxyalkylene) moiety contains oxypropylene and/or oxybutylene units, or a hydrocarbyl poly(oxyalkylene) aminocarbamate.Preferred Succinimide: The hydrocarbyl-substituted succinimide is a polyalkyl or polyalkenyl succinimide, where the polyalkyl or polyalkenyl moiety has an average molecular weight of 500-5000.Preferred Component: The nitrogen-containing detergent additive includes a Mannich reaction product obtained by condensing a polyalkylphenol with an aliphatic aldehyde and an alkylene polyamine. It includes amino aromatic ester of polyalkylphenoxyalkanol of formula (II) and polyalkylphenoxyaminoalkane of formula (III). The liquid hydrocarbon comprises a distillate fuel having a low sulfur gasoline blend stock (preferably hydrotreated straight run gasoline, fluid catalytic cracking gasoline, rerun alkylate, or reformate). The cell is a polymer electrolyte membrane (PEM) fuel cell.Preferred Composition: The additive is present at 25-2500 (preferably 35-1000) ppm. A fuel-soluble, non-volatile carrier is present at 25-2500 (preferably 35-1000) ppm. The distillate contains sulfur (less than 3, preferably less than 0.5 ppm).R17 = 1-30C hydrocarbyl;R18, R19 = H, 1-6C alkyl;B = amino, 1-20C N-alkyl amino, 1-20C N,N-dialkyl amino, 2-12 amine N and 2-40C polyamine;m = 5-100;R8 = -(CH2)n-NR13R14;R13, R14 = H or 1-6C alkyl;n = 0-1;R9 = H, OH, NO, or -NR15R16;R15, R16, R10, R11 = H or 1-6C alkyl;R12 = polyalkyl (Mw = 450-5000);R5 = polyalkyl (Mw = 600-5000);R6, R7 = H or 1-6C alkyl;A = B. EXAMPLE - Phenol (203.2 g) was added to a flask, and warmed to 40degreesC. Boron trifluoride (73.5 ml) was added dropwise. Ultravis 10 (RTM: polyisobutene) (1040 g) was dissolved in hexane (1863 ml). The polyisobutene was added to the reaction maintaining at 22-27degreesC. The reaction mixture was stirred for 16 hours. Concentrated ammonium hydroxide (400 ml) was added, followed by hexane (2000 ml). The reaction mixture was washed with water, dried under vacuum to yield 1056.5 g of a crude reaction product containing 80% polvisobutyl phenol.