Is My E82 128i/E9X 328i a SULEV or Regular LEV?
Are you unsure if your 2006-2011 E82/E90/E92 model is a SULEV model or not? This page should help you identify a SULEV E82/E9X model. First a little background. SULEV stands for Super Ultra Low Emissions Vehicle. It's a standard enacted by the California Air Resources Board (CARB) and similarly adopted by the federal government and other states. Nearly all BMWs qualify as LEV (Low Emissions Vehicle) but under law BMW's entire model range must meet certain low emissions targets. To raise their average while selling high-performance cars like the M5 and X5M, BMW has special SULEV models. In California particularly, a certain percentage of vehicles must be sold as SULEV spec or the manufacturer faces hefty fines. BMW developed a specific engine package that meets the SULEV standard - the BMW N51. If your E82 128i, E90 328i, or E92 328i was originally purchased in California, Connecticut, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont, Washington state, and Washington D.C. it will most likely come with the N51 SULEV engine. Having the SULEV spec is not a bad thing but certain components are different than standard N52 engines and you should be aware if you have an N51 engine.
Visually the N51 and N52 are identical. On the previous M56 SULEV and M54 engines in the E46 you could see a visual difference in the valve covers of each engine. That's not the case with the N51 and N52. The easiest identification is from the emissions label located on the underside of the hood -
N51 vs. N52 Differences Chart:
(originally published by BMW then modified by me)