An unleaded high octane gasoline composition exhibiting reduced gum formation and improved air intake system and combustion chamber cleanliness is provided comprising at least (A) one reformate fraction produced by a continuous regeneration type reformer and/or (B) at least one reformate fraction produced by a fixed bed type reformer, said unleaded high octane gasoline composition satisfying the following conditions: Z=(1/100)[.SIGMA.(ax)+(1/9).SIGMA.(by)]<0.010 wherein .SIGMA.(ax) is a summation of (ax) wherein (a) is content (vol %) of a fraction falling into reformate fraction A, (x) is content (vol %) of aromatic hydrocarbons having a carbon number of 11 or more in the fraction (a) and .SIGMA.(by) is a summation of (by) wherein (b) is content (vol %) of a fraction falling into reformate fraction B, (y) is content (vol %) of aromatic hydrocarbons having a carbon number of 11 or more in fraction B; the content of aromatic hydrocarbons having a carbon number of 7 to 8 being 30 vol % or more; and having a research octane number of 96.0 or more.

Ein unverbleiter hoher Oktanbenzinaufbau, der verringerte Gummianordnung und verbessertes Lufteintrittsystem ausstellen und die Brennkammersauberkeit wird mindestens (a) einen reformate Bruch enthalten zur Verfügung gestellt, der nach einer ununterbrochenen Regenerationsart Reformer und/oder (b) mindestens ein reformate Bruch produziert wird, der nach einer örtlich festgelegten Bettart Reformer, der besagte unverbleite hohe Oktanbenzinaufbau produziert wird, der die folgenden Bedingungen erfüllt: Z=(1/100)[.SIGMA.(ax)+(1/9).SIGMA.(by)