Fuel compositions and additives therefor

A method for controlling intake valve deposits in a gasoline engine comprising fueling and operating said engine with a fuel composition which comprises a major amount of hydrocarbons of the gasoline boiling range and a minor engine deposit-inhibiting amount of a fuel additive composition which comprises:

• a) a gasoline-soluble Mannich reaction product of (i) a high molecular weight alkyl-substituted phenol, (ii) amine, and (iii) aldehyde;
• b) a gasoline-soluble poly(oxyalkylene) carbamate;
• and
• c) a gasoline-soluble poly(oxyalkylene) alcohol, glycol or polyol, or mono or diether thereof.

A fuel composition for use in operating a gasoline engine therewith, which fuel composition comprises a major amount of hydrocarbons of the gasoline boiling range with which has been blended minor engine-deposit controlling amounts of:

• a) a gasoline-soluble Mannich reaction product of (i) at least one high molecular weight alkyl-substituted phenol, (ii) at least one polyamine, and (iii) at least one aldehyde;
• b) a gasoline-soluble poly(oxyalkylene) carbamate;
• and
• c) a gasoline-soluble poly(oxyalkylene) alcohol, glycol or polyol, or mono or diether thereof that has in its undiluted state a viscosity in the range of about 87 to about 98 cSt at 40.degree. C. and in the range of about 15 to about 19 cSt at 100.degree. C.
• in proportions of from about 0.5 to about 3 parts by weight of active Mannich base in a) and from about 0.5 to about 3 parts by weight of active carbamate detergent in b) per part by weight of c).