Page 2 of 2 FirstFirst 12
Results 26 to 36 of 36

Thread: Terrible Fuel Mileage

  1. #26
    Join Date
    Sep 2018
    Location
    Burnaby, BC, Canada
    Posts
    24
    My Cars
    1995 BMW 525iA
    So update to the situation, I filled about 70% fuel a little while back. Used about 35% so far and my mileage is up to 240KM. So fuel efficiency seems to have improved drastically since I swapped back to OEM plugs and pulled out those old and worn NGK Iridiums.

    Also moroza, I love your suggestion of the 525tds, but I don't think they were sold in Canada. And even if they were I'm sure it's virtually impossible to find one!

  2. #27
    moroza's Avatar
    moroza is offline MORΩN ΛABIA BMW CCA Member
    Join Date
    Sep 2006
    Location
    BFE
    Posts
    11,090
    My Cars
    E34T
    They weren't, but you're not far from a lot of importers, and the 525tds is well over the 15 year limit.

    What plugs, exactly? BKR6EK or something else?
    Last edited by moroza; 06-12-2019 at 09:46 PM.

  3. #28
    Join Date
    Sep 2018
    Location
    Burnaby, BC, Canada
    Posts
    24
    My Cars
    1995 BMW 525iA
    Yeah there's a 525tds touring for sale right now in my city, but he wants $16K. Which I mean I would rather spend on something newer in all honesty.

    I put in the NGK BKR6EK. My local parts store said they were listed as the OEM plug in their system.

  4. #29
    Join Date
    Apr 2007
    Location
    Nashville, TN
    Posts
    1,081
    My Cars
    E34, E30, 240sx
    Mine is all city and I get about 19mpg with my 525. I feel like the car is underpowered with this engine but I also have 327k miles on it.

  5. #30
    Join Date
    Sep 2012
    Location
    El Paso Del Norte, TX, US
    Posts
    438
    My Cars
    ‘15 F31d Msport
    Quote Originally Posted by moroza View Post
    Actually, a lot of the most efficient cars made are from the 80's. While there have been some mild improvements in engine efficiency since the early days of EFI, it's been more than outpaced by weight gain, such that US average fuel economy peaked in 1985, followed by a decline until 2005 or so when hybrids started to get common. E34 don't get mediocre economy because they're old, it's because they're 6 or 8-cylinder, RWD, not especially light, and not especially aerodynamic. A newer car with similar dimensions including displacement and cylinder count, such as an E60 535i, gets about the same mileage - 2010 535iM 16 city, 26 highway - albeit with a lot more power (nothing a turbo M30 can't do). An 80's Civic will get better economy than any petrol BMW, and likely better than a new Civic for that matter. You want city economy? FWD, light weight, small and few cylinders, diesel, driving style with a lot of coasting. You want highway economy? Same deal, except gearing matters more, weight matters less, and aerodynamic drag matters a lot more. Want better economy without driving an underpowered tin can? Turbodiesel. Hence the 525tds suggestion.
    And yet here I am pulling mid 30s at 80mph with my e46 325it SULEV, which is about the size and weight of an e34it and has 200k miles on it.
    I get about 18-20 in my usual short distance driving (work is 10 minutes or less away).
    There were MASSIVE gains based in engine design and ecu programming and power. The e34 is rather crude by comparison... but also easier to work on!
    If I were to give my Touring a first name, I'd probably name it "Alan".
    Mostly because I like puns.
    Mutual Admiration Society #5

  6. #31
    Join Date
    May 2017
    Location
    Perth, Western Australia
    Posts
    1,100
    My Cars
    09/90 E34 525i (M50)
    Quote Originally Posted by fo3 View Post
    To be honest I expected someone to post something saying the OP is doing something wrong and maybe I'd learn something
    I learnt something. Finally fixed my last vacuum leaks (oil cap - didn't know that could be a leak - and fuel pressure regulator manifold o ring - the fitting is NLA for early cars so I didn't dare touch it again), put in new fuel injectors as I always suspected them leaking. I just used cheap $100 a 6 pack set of chinese fuel injectors too.

    My economy in suburban driving has gone from 12.6L/100km (18mpg)to 10.8L/100km (21mpg). Seems to drive fine too. I'll start the day ~ 10.6-10.8l/100km on the OBC with a cold engine and drive how I want accelerating past fast lane road hoggers etc which makes the OBC go as far as 11- up to 11.2L/100km then I'll calm down. By the time I get home it's back down to 10.8 or lower. So consistently around 21mpg in stops start urban traffic.
    Previously it would start high after a reset and some calm driving come down to 12l/100, but would keep getting higher and higher every subsequent day. But now after a couple of weeks it's reliably hanging around 11 or less.

    Pretty suprising cheap injectors would make that much of a difference as I haven't even gone on any long trips to try improve economy. In fact the opposite, I've done heaps of short drives doing brake and suspension changes and adjustments, and a couple of local shop runs which before would make my OBC show 13l/100km average in a hurry. Get new injectors everybody - also make sure you have fixed ALL vac leaks
    Last edited by fo3; 09-19-2019 at 10:06 AM.

  7. #32
    moroza's Avatar
    moroza is offline MORΩN ΛABIA BMW CCA Member
    Join Date
    Sep 2006
    Location
    BFE
    Posts
    11,090
    My Cars
    E34T
    Quote Originally Posted by Onizukachan View Post
    And yet here I am pulling mid 30s at 80mph with my e46 325it SULEV,
    I doubt. What are some actual distance/fillup numbers?

    Anyway, there are some people claiming 30's highway out of E34 525iT as well.

    which is about the size and weight of an e34it
    About 300lb lighter and considerably more aerodynamic, not to mention taller-geared on the highway...
    and has 200k miles on it.
    Irrelevant. If anything, all the bearings spin more freely from the wear.
    I get about 18-20 in my usual short distance driving (work is 10 minutes or less away).
    ...which is why your city economy is a hair to no better than a 525iT.
    There were MASSIVE gains based in engine design and ecu programming and power.
    Yeah, but the breakthroughs happened in the 80's, and until GDI and lean-burn (as much a function of mechanical as computational design) came along, the improvements have been slight to stagnant to (in some cases, due to emissions) reversed. Holding weight, displacement, and cylinder count constant, the marginal gains in efficiency are mostly due to better gearing and aerodynamics. Holding power constant, the meaningful gains are due to smaller and fewer-cylinder turbo engines replacing their predecessors.
    Last edited by moroza; 09-19-2019 at 01:06 PM.

  8. #33
    Join Date
    Jan 2017
    Location
    Amman, Jordan
    Posts
    227
    My Cars
    1995 BMW 525i Touring
    from years of experience, I have a 95 525iT for the past 23 years. using 90 Octaine fuel I get terrible milage and knocking from the engine, when I use 95 octane or use octane booster on the 90 I get 7.5KM/L city and around 12KM/L highway.

    the car has 225k KM, but I did change the engine about 5 years ago with a M52B28 with 30K KM using the original AIrintake, sensors and DME of the M50B25. mileage has improved slightly.

    my 2 cents.
    Last edited by zkd; 09-21-2019 at 03:49 PM.
    E34 525i Touring 1995, M52B28 LSD... fully restored.


  9. #34
    moroza's Avatar
    moroza is offline MORΩN ΛABIA BMW CCA Member
    Join Date
    Sep 2006
    Location
    BFE
    Posts
    11,090
    My Cars
    E34T
    Jordan probably uses RON octane, not AKI or MON. Your 90 is similar to our 85-86, and 95 is 90-91.
    Last edited by moroza; 09-21-2019 at 05:33 PM.

  10. #35
    Join Date
    Jan 2017
    Location
    Amman, Jordan
    Posts
    227
    My Cars
    1995 BMW 525i Touring
    Quote Originally Posted by moroza View Post
    Jordan probably uses RON octane, not AKI or MON. Your 90 is similar to our 85-86, and 95 is 90-91.
    true but I didn't realize that until you told me.
    E34 525i Touring 1995, M52B28 LSD... fully restored.


  11. #36
    Join Date
    Sep 2018
    Location
    Los Angeles
    Posts
    79
    My Cars
    1990 535i Turbo Widebody
    I got the same problem, I fill up the tank, my OBC range says 200 Miles..... then as soon as I drive off from the gas station I literally start dropping a mile every 400-500 feet.... 200, 199, 198, 197..... However, the MPG reads 16.8-18.1 MPG.... it's almost like they are working in different fuel systems lol...
    Last edited by E34DinanZeemax; 09-26-2019 at 09:27 PM.
    <img src="https://ibb.co/D76PKCx" border="0" alt="">

Page 2 of 2 FirstFirst 12

Similar Threads

  1. Terrible fuel mileage..
    By atlantisvip in forum 1991 - 1999 (E36)
    Replies: 1
    Last Post: 11-10-2006, 11:12 AM
  2. Poor fuel mileage?
    By ryan_george in forum 1983 - 1991 (E30)
    Replies: 3
    Last Post: 06-10-2004, 10:23 AM
  3. Fuel Mileage on a 328
    By SJTrance in forum 1991 - 1999 (E36)
    Replies: 13
    Last Post: 10-13-2003, 09:39 AM
  4. Fuel Mileage?
    By paul e in forum Forced Induction
    Replies: 17
    Last Post: 03-13-2003, 05:32 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •