A fuels matrix with aromatics and mid-range volatility (T50) independently varied was applied to 2 fleets (catalyst and non-catalyst) consisting of vehicles currently driven in Europe.For the catalyst fleet, reducing aromatics or T50 gave lower HC/CO. After catalyst light-off, decreasing aromatics gave more NOx sufficient to determine the direction of the composite cycle response. This is fully consistent with recent EPEFE results (future technology vehicles), confirming the general applicability of the EPEFE conclusions.Mostly, HC/CO responses from the non-catalyst fleet were directionally similar, though statistically less robust. However, at high volatility, reducing aromatics increased HC/CO. NOx was reduced by lowering aromatics and, to a lesser extent, mid-range volatility.