As Lasse notes the use of older automobiles means less fuel economic models.
But there are two other points to look at. Firstly European emission standards as usually more stringent than North American ones, meaning their older cars are not as fuel inefficient as NA older cars. Secondly the longer usage of automobiles ensures that cars are used for their natural lifetimes rather than consumers continually replacing still decent cars for newer models. While older cars are less fuel efficient continual usage ensures that they are less cars imported into the country and less cars being scrapped (as they are replaced). A fairly reasonable off set in my opinion.
But there are two other points to look at. Firstly European emission standards as usually more stringent than North American ones, meaning their older cars are not as fuel inefficient as NA older cars. Secondly the longer usage of automobiles ensures that cars are used for their natural lifetimes rather than consumers continually replacing still decent cars for newer models. While older cars are less fuel efficient continual usage ensures that they are less cars imported into the country and less cars being scrapped (as they are replaced). A fairly reasonable off set in my opinion.