Fouling in a multi-port, electronically controlled fuel injection system is reduced and/or prevented by using a fuel contg. a tert. amine of formula NR1R2R3 (I), where R1 is a 6-24C alkyl, aryl, cycloalkiphatic, heterocyclic, substd. alkyl or substd. aryl gp., and R2 and R3 are 1-24C substd. alkyl, aryl, cycloaliphatic or heterocyclic gps. Also claimed are fuels contg. (I) and a demulsifier (II), and fuels contg. (I) and an amino oxide antifouling agent (III). Pref. the fuel is gasoline (esp. unleaded). (I) is of formula R'1N(CH2CH2OH)2, where R'1 = coco alkyl, tallow alkyl, stearyl or oleyl. (II) is an acylated polyglycol (e.g. 'Tolad T-284'), a mixt. of alkylaryl sulphonate, polyglycol and oxyalkylated alkylphenol-formaldehyde resin (e.g. 'Tolad T-286'), a mixt. of oxyalkylated alkylphenol-formaldehyde resin and polyglycol (e.g. 'Tolad T-326') or an oxyalkylated alkylphenol-formaldehyde resin (e.g. 'Tolad T-500' or 'Nalco 5455'). (III) is of formula R4R5R6N-O, where R4-R6 are as defined for R1-R3. 
BRENNSTOFFZUSAMMENSETZUNG FUER MEHRSPALTIGE BRENNSTOFFINJEKTIONSANLAGEN UND DEREN VERWENDUNG.