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Thread: Horrific Fuel Economy on N54 E60

  1. #1
    Join Date
    Feb 2019
    Location
    Cleveland, OH
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    2
    My Cars
    2010 BMW 535xi E60

    Horrific Fuel Economy on N54 E60

    I just bought a 2010 535xi E60 with 100k miles and have been doing mostly city driving since I got it. I expected the city fuel economy to be bad, but not quite this bad. According to iDrive, I've been getting about 8mpg with 93 octane fuel (and I have recorded similar figures at the pump). Are there any common mechanical issues that could lead to this, or is this just the true fuel economy of the N54 E60? The tire pressure is fine, car is mostly empty, the engine oil and valve cover gasket were changed 2 weeks ago.

    I've considered changing the air filter, but I'm waiting to get the DCI until I get the JB4 tune as well.

  2. #2
    Join Date
    Sep 2007
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    New York
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    1974 2002, 2009 128i
    Are you seriously not willing to change an air filter before dropping money on tuning a car that's currently returning 8MPG? Something's obviously very wrong - why don't you figure that out and fix it properly before trying to upgrade it? Get the codes read (properly, with a BMW-specific code reader) and maybe pay for an hour of diagnostic time to get a handle on what's going on.





    Life's tough. It's tougher when you're stupid.
    -John Wayne

  3. #3
    Join Date
    Jun 2005
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    New England
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    F90 M5; E36 M3 Turbo
    8 mpg is too low unless you are stuck in traffic and not really going anywhere. I suspect there are some issues. I agree with using a quality scan tool with bmw specific software to pull codes, reset adaptions, etc. A lot of 10 year old BMWs look nice and are cheap compared to what they cost new, but have a lot of deferred maintenance and also need some repairs. Had our 08 535xi since 2011 and it has been a good car. Never gotten 8 mpg but I don’t drive in heavy city traffic. We average about 22, but that is mixed with mostly highway.

  4. #4
    Join Date
    Jun 2002
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    E39M5, E500 4WD
    My M5, with 8 throttle bodies and somewhere around 400 hp, gets a combined 20 mpg. The E500 does about the same, and the Subie, unfortunately, equals that too. Hell, I had a 650 hp 427 Camaro that got 13 city and 18 highway. In other words, yes you have a problem.

    With no additional information, I'm going to have to guess that your car isn't warming up properly, so it's staying in "Open Loop".

    This is just a wild assed guess.

    Your very best bet is to have a good BMW specialist technician look at the stored trouble codes, and at the live data. Some codes do not set a Check Engine Light, but will still be stored. Watching live data might show that (for instance), an intake air temp or engine coolant temp sensor is reading that the engine is stone cold, even when it's not.

    OR, maybe the intake passages need walnut blasting, or the injectors are dumping fuel.

    Get a good BMW specific scan tool on it, and see what you get.

    Do not modify the car until you fix it and verify everything is good.

    Personally, I'd have to advise against putting a JB4 tune on it anyway. Every single N54 car I've seen with this tune was broken so badly that the car was worthless. The N54 isn't exactly reliable, even in stock tune (as you've seen).

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  5. #5
    Join Date
    Feb 2019
    Location
    Cleveland, OH
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    2010 BMW 535xi E60
    Thank you very much for the responses. I plan to have the issue properly diagnosed before making any modifications.

    Another potential issue is that the weather is very cold and my commute is about 10 minutes long, so the engine may not ever heat up correctly. I have heard that this may pose long term threats and I should try to start the car before driving.

    Is it true that in open loop the engine will run very rich?

  6. #6
    Join Date
    Jun 2002
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    E39M5, E500 4WD
    All the above is somewhat true.

    Yes, the car will run significantly richer when in open loop. Open loop shouldn't last more than about a minute, though, if everything is working properly.

    I do not recommend starting and idling the car for any length of time before driving it. That's just wasting fuel. Certainly, you should DRIVE your car for longer, at least a couple of times a week, to bring everything up to full operating temperatures, and burn off condensation inside the engine. It's a really good idea to do an "Italian Tune Up" at least once a week. (After driving the car for at least fifteen or twenty minutes, find somewhere to accelerate HARD, through three or more gears, to high rpms in each gear....then repeat) Your engine will be happier for that.

    The N54 clogs intake passages in the cylinder head, because it's direct injection. This will cause terrible mileage, and potentially misfiring and poor running. Nothing will fix this except walnut shell blasting.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  7. #7
    Join Date
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    The amount of goo I scraped out of my intake ports was incredible. I could not blast the carbon until I got most of the goo out. If it has not been done on your car, do it. Good opportunity to do some other maintenance as well like the oil filter housing gasket, valve cover gasket, oil cooler to housing gasket, coils, plugs, etc.

    I have been running a JB4 for years. It’s great! Wakes the car up. Cobb makes a flash tune, as do others, that are also worth looking into. Certainly make sure your car is sorted out and properly serviced and maintained before adding power.

  8. #8
    Join Date
    Jun 2002
    Location
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    E39M5, E500 4WD
    I'm glad to hear your JB4 is working for you, my friend ! Perhaps it's not the tune, but neglect, that has resulted in the catastrophes I see so often.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  9. #9
    Join Date
    Jun 2005
    Location
    New England
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    F90 M5; E36 M3 Turbo
    The only side effect I noticed from the JB4 was misfires. Figured it was worn gaps on the plugs. Changed them but the problem remained. The misfires were due to failing coils. The coils worked fine at stock boost, but not at higher boost. I changed them and the problem went away. I used S55 coils but new N54 would have been fine. I have read that weakening coils is common on these cars and often shows up when the cars are modded.

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