The paper outlines the OR trends of European and Japanese cars found in the European market place over the last five years. The consistently high proportion of critical models (at the 98 RON European Premium grade level) is highlighted, possibly reflecting the consequences of exhaust emissions and economy tuning brought about under the influence of tightening European legislation. However, the significant number of cars suffering from ignition over-advance is also investigated, this aspect being felt to be of increasing relevance.
Whilst the importance of front end octane number as a gasoline parameter is shown to be declining slowly, the continuing large number of vehicles conscious, to a slightly increasing extent, of high sensitivity and/or olefin content is emphasized.
Finally, the deleterious effect of lowering lead concentration is clearly demonstrated, particularly under the high engine speed conditions commonly encountered by small-engined European vehicles.