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Thread: Low MPG

  1. #1
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    Low MPG

    So I have a 98,000 528i here. Year 1999. Recently I have just been curious to check MPG and it's between 13-14. I'm usually driving around here in the Orlando, Florida area so city. However I've read on the manual that I should be getting 18mpg in cities.

    So far on the car

    I have changed

    Spark Plugs (Denso)
    Usually/Always get 93 Gas at Costco
    Entire Cooling System overhaul (new radiator, etc.)
    2 new Pre-cat oxygen sensors.
    New Intake boot(s)
    Regular Oil Changes (5W-30) Synthetic/High Milage


    Honestly I don't know what is wrong. I thought oxygen sensors would fix it but it didn't. Anyone have suggestions? An oil leak was recently fixed.

    Thanks
    Tek


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  2. #2
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    Is this the mpg the car calculates or have you calculated it yourself

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  3. #3
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    Quote Originally Posted by ColtonBH View Post
    Is this the mpg the car calculates or have you calculated it yourself

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    MPG the car calculates. Is it a dummy? Or is it just not accurate like the thermometer?


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  4. #4
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    Do the old-fashioned arithmetic on a full tank. What are the fuel trim numbers?

    The external temp measurement is generally quite accurate. Bear in mind that it is primarily measuring the road surface.


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  5. #5
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    Quote Originally Posted by tek.to View Post
    MPG the car calculates. Is it a dummy? Or is it just not accurate like the thermometer?


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    It's an average...and depending on how often you reset the calculation and how you fill the tank (a few dollars at a time...or complete fill-ups etc)...the OBC's MPG calculation can vary from your own calculation.

    In the chart below of my e53 from a few years ago (I keep/kept the same chart for my e38 & e39 when I had it)...and the same thing occured with them, too. The OBC's displayed MPG can vary by a gallon or more vs my actual MPG calculated at each fill-up. But if you look at the bottom of the columns...you'll see by the end of the year...there's only a 0.37 difference between the two. So the OBC isn't really that far off (in my cases) from the actual over a long time averaging cycle. But the week to week...or fill-up to fill-up calculation can be different by a larger amount:

    {E53 = difference of 0.37 between actual and OBC display}



    {E38 = diiference of 0.48 between actual and OBC display}

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  6. #6
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    Quote Originally Posted by edjack View Post
    Do the old-fashioned arithmetic on a full tank. What are the fuel trim numbers?

    The external temp measurement is generally quite accurate. Bear in mind that it is primarily measuring the road surface.
    Ohh ok. Thanks. Yea I usually fill up the entire tank once the marker reaches about 1/8 full and also reset it

    I'll calculate manually myself thanks based on the chart below the Car Calculator for his E38 also says 14.8 etc.., so mines probably not accurate either




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  7. #7
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    Yeah, that's the first step to tracking your gas mileage— never trust the onboard computer. I've been tracking my fillups with Fuelly for years now, it's way more accurate than the onboard MPG display. I've been averaging 14.5mpg – 20mpg in my 540it, depending on how much city driving I do.
    1995 525i 5-speed - Thread

  8. #8
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    Do you use the high mileage oil like m1 5w-30 synthetic high mileage?
    (Noticed you put high mileage on your original post)

    That stuff is very thick and could potentially make your engine run rougher and use more gas from cold starts until it gets good and hot and thins out. I'd try something different if that's the case.

  9. #9
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    Quote Originally Posted by WBAD530i View Post
    Do you use the high mileage oil like m1 5w-30 synthetic high mileage?
    (Noticed you put high mileage on your original post)

    That stuff is very thick and could potentially make your engine run rougher and use more gas from cold starts until it gets good and hot and thins out. I'd try something different if that's the case.
    Oh this is the stuff I use: (thing on the right)

    I've heard OW-40 works too but I'm not too sure. I just thought the high mileage would be better since my car has 98,000 miles and btw the high mileage was more expensive too, but more expensive doesn't mean always better.


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  10. #10
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    Methinks "high-mileage oil" is a marketing thing.


    Ed in San Jose '97 540i 6 speed aspensilber over aubergine leather. Build date 3/97. Golden Gate Chapter BMW CCA Nr 62319.

  11. #11
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    Yep that's the stuff. Its like molasses. I used it after my chain guide job and it had a hard time operating the vanos properly. It was a bit cold around that time and the car had been sitting so that didn't help but I noticed a difference after I swapped it out with 0w-40.

  12. #12
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    Quote Originally Posted by WBAD530i View Post
    Yep that's the stuff. Its like molasses. I used it after my chain guide job and it had a hard time operating the vanos properly. It was a bit cold around that time and the car had been sitting so that didn't help but I noticed a difference after I swapped it out with 0w-40.
    Ok so you recommend ow-40?


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  13. #13
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    I run 0w-40. It's perhaps the most popular oil, and I have had good results

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  14. #14
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    Yeah 0w-40 or even regular 5w-30 thats not the high mileage goop. It's just oil in the end, but our cars seem to like it thinner to get everywhere it needs to be.

  15. #15
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    Check your tire pressure. I would also take a look at your air filter to see if there is a bunch of crud on the filter.

  16. #16
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    Clean your MAF.

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  17. #17
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    Quote Originally Posted by bE34ST View Post
    Clean your MAF.
    Yea I have Cleaner the MAF and also pumped tire pressure according to specs on my driver door.


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  18. #18
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    Jeezzz... You guys run thin oil!

    I run 15-50 Mobil-1 in my S52US... No vanos or other issues although it does not get driven in the winter (no snow/ice/salt but COLD does not slow me down)

    And my F10 OBC fuel economy is way off from the old-fashioned calculations as well. No OBC in my ti.
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  19. #19
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    Quote Originally Posted by tiMASTER View Post
    Jeezzz... You guys run thin oil!

    I run 15-50 Mobil-1 in my S52US... No vanos or other issues although it does not get driven in the winter (no snow/ice/salt but COLD does not slow me down)

    And my F10 OBC fuel economy is way off from the old-fashioned calculations as well. No OBC in my ti.
    Well I do have the M52TU lol


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  20. #20
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    Quote Originally Posted by tiMASTER View Post
    Jeezzz... You guys run thin oil!

    I run 15-50 Mobil-1 in my S52US... No vanos or other issues although it does not get driven in the winter (no snow/ice/salt but COLD does not slow me down)

    And my F10 OBC fuel economy is way off from the old-fashioned calculations as well. No OBC in my ti.
    The recommended oil for the M62tu V8 is 0W40, and my engine really does seem to run best with 0W40. I've experimented with thicker oil like 10W40 and it didn't really make anything better.
    1995 525i 5-speed - Thread

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