The BMW SULEV Chronicles – What Does Super-Ultra-Low-Emission-Vehicle Really Mean

BMW, producer of the Ultimate Driving Machine, generally doesn’t do anything halfway.  When a large portion of their upscale buyers suddenly found themselves in areas that either required low emissions or offered incentives, the Germans kicked into action to produce something to whet the appetites of the power that be – the BMW SULEV. The result is a vehicle that has extremely low CO2 and Gasoline evaporative emissions.  These, of course, come at a cost, which is the complexity of several added or changed systems.  Although they might not be obvious, if you are an enthusiast looking to tune, or a budget-oriented consumer looking to keep maintenance costs down, being able to recognize the differences between standard and SULEV vehicles can make a huge difference when buying your next BMW, or caring for your existing one.

BMW SULEV Fuel Tank Comparison

BMW SULEV – The Beginning

The year 2003 marks the beginning of the saga, when the E46 was outfitted with a different version of the venerable M54 engine, designated the M56.  There were several changes that were made to suit requirements for SULEV designations, as well as PZEV (Partial Zero Emissions Vehicle).  Cars with these tags can be eligible in some states for subsidized credits, so be sure to know if you are registering a BMW SULEV, ULEV, or PZEV car in a place that offers these perks.

California, New York, Massachusetts (2003), and Vermont (in 20The 04) were the first recipients of M56 equipped cars.  Since then, many BMW vehicles were equipped with SULEV equipment, up to current.  After the E46, the E90 family of cars received new engines as well as the E80 1 series and a few others.  The N52 is the standard workhorse in these cars, with the N51 carrying the SULEV badge.  Currently, with the F series body types, the SULEV engine to look out for is designated as the N26.  In these later cars, the line between standard and SULEV is beginning to blur, as BMW is incorporating more and more standard components throughout all models to make for a greener overall product line.

Every state (and country) handles low emission vehicles differently, and I’m not going to go into that much here.  Rather, being a car parts company, it’s important to be aware of the PARTS you may need, and the changes BMW made to its cars to categorize them as Super Ultra Low emissions.

So what is actually different on a BMW SULEV?

  • Intake/airbox.  The airbox on BMW SULEV cars includes an additional carbon chemical filter that prevents unburned hydrocarbons from the engine internals from floating out the intake system and into the atmosphere.  Additionally, the PCV system hooked up to the intake system and valve cover is all different, made of different materials and featuring extra components and redesigned oil separators.
  • Engine Mechanicals.  Subtle but fundamental changes have been made throughout the engine internals to lower the compression and increase efficiency.  This includes different pistons with redesigned crowns, and a different cylinder head with larger combustion chambers.  The magnesium valve cover on the N52 is replaced with a plastic one, with extra integrated PCV components.
  • Exhaust.  Because a cat must be warmed up before it begins doing it’s magic, SULEV BMWs have positioned a catalytic converter directly at the end of the exhaust manifold.  That ensures the quickest warm up time, and the least amount of dangerous emissions to make it out the tailpipe.  A third cat has also been added on the underbody of the car, so expect the exhaust system on these cars to be completely different.


  • Fuel system.  The fuel system in BMW SULEV cars is completely reworked by replacing conventional plastic fuel lines with stainless steel.  On the E46 M56 engine cars, a bad fuel pump would require replacing the entire fuel tank and associated lines, a dealer service that could exceed $8,000.  Because of the outrage associated with this, BMW was required to extend the warranty (described below) due to the ludicrous maintenance costs.  In later cars (E90 on), the fuel pump and fuel filter went back to a more standard style that can be independently replaced.  In N26 engines, the high pressure fuel pump has a slightly different design to allow quicker relief of pressure when the engine shuts off to prevent the possibility of pressure leakage.  Assume different replacement parts to be installed from the fuel filler neck all the way to the injectors.
BMW SULEV Radiator

The black manganese coating (and subsequent sensor) is designed to help convert Ozone to pure Oxygen

  • Cooling.  If you are looking for a single telltale sign that your car carries these emissions components, a sure-fire way is to take a look at the radiator.  SULEV BMW radiators have a black coating on them with an integrated sensor attached to the core.  The coating is a manganese oxide material that is designed to convert Ozone (O3, an unbreathable greenhouse gas) into O2, the more likable, more breathable version of oxygen.  I suppose the theory is that if enough cars have these equipped, they can help filter harmful ground-level ozone into plain oxygen.

If you were to require a radiator change, it must be this specially coated radiator or else the sensor will trigger an error code.  The sensor specifically detects whether or not the coating on the radiator is doing its job, and if you swap to a standard aluminum radiator, you won’t be passing emissions or inspection due to a CEL.

BMW Sulev Differences

Because of the extra expense of maintaining a BMW SULEV, an extended warranty has been instated on all SULEV specific parts of 15 years or 150k mi.  That is pretty solid when it really comes down to it, but due to the age of many of the earlier SULEV vehicles, and the impending failure of SULEV components on freshly out of warranty newer vehicles, it is important to know that you have a SULEV car before you start buying parts, or you are in for a ride down long and confusing highway.  Additionally, when comparing these vehicles to non-SULEV counterparts, drivers can expect a slight dip in sporty performance, due to the extra filters, catalytic converters, and lower compression.  All things to keep in mind when shopping around for your Next BMW, or maintaining your current one.

How do I know if MY car is a SULEV?

SULEV BMW’s are quickly becoming the standard, with a large number of US-bound cars bearing these emissions systems.  As mentioned before, the SULEV engine for the E46 is M56, the E90 series cars are powered by N51 SULEV engines, and for the new F30/F31 chassis, the SULEV engine is the N26. More easily, if you are curious whether or not your car has one of these engines, check this out.  In the engine bay, there is an emissions tag (I’m sure you’ve seen it).  If it is indeed a SULEV, it will state it somewhere on this tag, either by listing a SULEV engine or specifically stating the car is SULEV.

This E46 emissions plate alludes to the M56 engine, which denotes a SULEV equipped vehicle

You may also come across ULEV, which simply stands for Ultra-Low Emissions Vehicle, which is not as extreme as their SULEV counterpart.

18 thoughts on “The BMW SULEV Chronicles – What Does Super-Ultra-Low-Emission-Vehicle Really Mean
  1. Mike

    I would like appreciate knowing if anyone has information on whether the N51 cylinder head requred redesign, as did the head for the N52 engine. BMW reported that new cylinder heads were used by the end of November 2008 — apparently to deal with the hydraulic ticking issue (insufficient oil delivery through passages?}. Are N51’s plagued with the same issue?



    • Bryan

      In my little opinion, most bmw engines have this issue. Used bmws with ticking across the board from n52s , n54s, even m54s. 2019 now so n54s and others seeing it. Bmw will say its a normal sound from an inline 6. Hah such bs. I wouldn’t say bmw engines are plagued tho .. they just require a particular type of care/maintenance..esp after 50k miles, which doesn’t seem to happen as often as it should. Lifter tick in a used Bimmer tells you maybe it didn’t have the greatest care. I see lifter ticking as almost normal but it is telling you there’s a problem! No immediate worries .. Needs attention before it exacerbates tho. Causes like a progressive issue .. loss of oil pressure (lost boost in turbos) esp after the engine is warmed…leading to higher likelihood of cam(s) and or ledges issues.. causing eventual knock/CEL & limp and prom other things on the way like injectors/fuel trim issues or hpfp issues etc. Lifters under the engine on both sides (24) develop wayyy too much play ..causing the ticking. I have a vid of this play if needed? I don’t even know how much there’s to do to help it but once the cams and ledges fault, you can replace all the lifters w/ little to no extra labor. Hope this helps

    • Adam Goral

      Depending on your state, SULEV is likely to be installed on the newer F30 body style cars starting in 2013. Check your emissions plate to see if it states the car is SULEV

  2. Andrej


    Maybe anybody know, what are the values of CO2 in SULEV BMWs? I have 428i convertible and I can’t find this information nowhere.
    Values for Europeans BMW 428i are between 157 and 164g/km, but SULEV should have lower, am I right?

    Thank you in advance.

    Kind Regards,

  3. Brian L.

    is a 2011 328i xdrive sulev covered by the 15yrs/150000K miles regardless of state purchase or registration? i have seen reference that it must be purchased/registered in specific states for this warranty to be effective.

  4. Bryan

    Great article, thank you. You mentioned SULEVs would cost more. Wouldn’t SULEV parts last longer, such as the aluminum gas lines versus BMW’s standard rubber gas lines? The SULEV’s electronic turbo waste gates (versus hydraulic powered gates in n20/26) and many others, seemingly, are BMW resolutions for their typical problems.. Therefore, general maintenance costs would seem to be lower overall? I realize a given part may cost more than the standard versions (like the aluminum lines) but these parts do last significantly longer. Seems SULEV are more reliable as a result of their differences. I’m curious if others feel SULEVs generally cost more to maintain (without a warranty) than BMW’s standard versions? I know I could have used some of my f30 aluminum lines on my 2008 n54.. would have save me bookoo. But maybe I’m missing something? Thanks

    • Adam Goral

      Bryan, this is a great observation. Yes it is true that in the attempt for the ultimate sealed system SULEV parts are built with more longevity in mind. Shame the wouldn’t just do that anyway. However, making money means buy cheap sell expensive which most OEM’s these days have perfected the art of planned obsolescence. Regardless, in the early days of the BMW SULEV, many of your replacement parts would cost significantly more. Currently, SULEV is far more ubiquitous which means more plentiful parts and less cost associated with having rare trim options. In the end I wouldn’t say SULEV costs more per say, just that you will find that parts will be different from non-SULEV vehicles and that always has the potential to be more expensive. Who knows, maybe we’ll see a reversal in this where non-SULEV components become the expensive outliers.

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