<p>In terms of emissions, LEV > ULEV > SULEV > PZEV (as in LEV has more emissions than ULEV, etc.). However, all emissions categories for cars are tiny fractions of the allowed emissions from a decade or few ago. It is to the point where if you end up behind a 1970s car, the emissions smell is overpowering – and then you realize that all cars were like that in the 1970s.</p>