A fuel composition has a major portion of hydrocarbons boiling in the gasoline range, at least 1,200 ppm by weight of a detergent, and at least 2,400 ppm by weight of a mineral carrier fluid. The detergent is a hydrocarbyl-substituted amine or polyamine having at least one basic nitrogen. The weight ratio of mineral carrier fluid to detergent of the fuel composition is at least 2:1. Preferably, the detergent is present at a concentration of at least 2,000 ppm by weight, and the weight ratio of mineral carrier fluid to detergent is at least 4:1. Preferably, the detergent is either a polybutene amine or a polybutene succinimide.