Gasoline composition for reducing intake valve deposits in port fuel injected engines

A method for operating an electronic port fuel injected engine on an unleaded fuel compatible with carburetor and throttle body injected engines which comprises introducing into an electronic port fuel injected engine with the combustion intake charge an effective amount to reduce intake valve deposits in the electronic port fuel injected engine of a mixture of (a) about 2.5 ppmw or higher of basic nitrogen based on the fuel composition in the form of an oil soluble aliphatic alkylene polyamine containing at least one olefinic polymer chain attached to at least one nitrogen or carbon atom of the alkylene radical connecting the amino nitrogen atoms and said polyamine having a molecular weight of from about 600 to about 10,000;

• and (b) from about 75 ppmw to about 125 ppmw based on the fuel composition of at least one component selected from (i) a polymer of a C.sub.2 to C.sub.6 monoolefin, (ii) a copolymer of a C.sub.2 to C.sub.6 monoolefin, (iii) the corresponding hydrogenated polymer or copolymer, (iv) an oil soluble poly(oxyalkylene) alcohol, glycol or polyol or a mono or di ether thereof, ether thereof, which has the formula R.sub.1 --O--(R.sub.2 O).sub.n --R.sub.3 wherein R.sub.1 and R.sub.3 each independently is a hydrogen atom or an aliphatic, cycloaliphatic or mononuclear aromatic hydrocarbon group of up to 40 carbons atoms, R.sub.2 represents an alkylene group and n is an integer of at least 7, and (v) a naphthenic or paraffinic oil having a viscosity at 100.degree. C. of from about 2 to about 15 centistokes, the weight ratio of as basic nitrogen to (b) in the mixture being in the range of about 0.0200 or higher.