1st Gen R53 Cooper S Terrible fuel economy, any ideas what it could be?

Discussion in '1st Generation: 2002–06 R50, R53 & 2004–08 R52' started by nismo4life, Jul 2, 2014.

  1. nismo4life

    nismo4life New Member

    Jan 31, 2012
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    So this time last year I was getting 31-34 on the highway. Since then I've changed literally nothing on the car except oil.

    Mileage is 150k, and in the last 15k I've done:
    -Fuel Filter
    -BPV
    -TB
    -Cleaned Unifilter
    -Upstream Map
    -Plugs (checked gap, its fine)
    -Wires
    -Optima 34R
    -Many other gaskets/seals
    -Reset ecu, many many times.

    With the exception of the only variable between last time and this time being I was on Conti all seasons, now I have lighter wheels with NT-01's that are down to 2 grooves, anything else you think could be causing this? Could the tires really drop fuel economy by 6 mpg's??

    Fwiw I had a CEL that lasted FOREVER. Its when the mpg's originally dropped in October when it came on. I finally was able to pin point it down to a torn BPV diaphragm and had it fixed. CEL gone, and all those new components and the car still gets shitty mileage. (Should be noted, CEL has been off for ~2,000 miles).
     
  2. Dave.0

    Dave.0 Helix & RMW Powered
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    Its Summer and you are driving with a heavier right foot? :p:devil:

    Oh and anything near 30 MPG is great, as for me I am lucky to get 20 MPG.
     
  3. MCS02

    MCS02 Moderator
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    Perhaps it the lose nut behind the wheel? Also I have been told by nice men in uniform that if I keep pushing the long skinny pedal to the floor it would cost me more the MPG. :D

    Have you changed the fuel you use?
     
  4. nismo4life

    nismo4life New Member

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    #4 nismo4life, Jul 2, 2014
    Last edited: Jul 2, 2014

    Lol. I wish it was because I'm laying on it. I used to be able to get a 24mpg mix if I had some fun. 21mpg if I REALLY stood on the gas all the time, but almost always got 31+ highway cruising. This was a 426 mile all highway road trip, and I never saw above 27mpg on the way there or back. Never saw over 8psi (have a 15% pulley).

    As for the fuel, I've ran various brands and locations fuel. Still no difference. Always 93 though with an exception in Northern Maine where they don't believe in 93 lol. Oh and fwiw I also ran a bottle of Techron through the tank, and an IV drip (similar to sea foaming) with no change.
     
  5. Dave.0

    Dave.0 Helix & RMW Powered
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    Check your tire pressure when its warm.
     
  6. Crashton

    Crashton Club Coordinator

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    Hit 31 MPG once, usually it's 30 MPG. It town I'm at 27 MPG. If your tires are smaller in circumference you mileage will be wrong & screw with your calculation for mileage.

    Do you have a brake dragging?
     
  7. nismo4life

    nismo4life New Member

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    Don't smell any brake/hear anything so I don't believe so. Doesn't feel like it either but I will still check it out. Doing the poor mans R56S conversion soon. Tire size is 215/45/17.

    Last I checked I had set them at 35 psi once warm. Haven't noticed the TPMS light, but I'll check again.
     
  8. wmwny

    wmwny Well-Known Member

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    I run my wife's same size tires at 35..cold. She also gets crappy mileage, but then, she only drives around 18 mph!:lol:
     
  9. ZippyNH

    ZippyNH Well-Known Member

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    #9 ZippyNH, Jul 2, 2014
    Last edited: Jul 2, 2014
    Feel your brakes/tires/rims for excess heat....
    I'm thinking one will be hot from a dragging brake pad.

    Edit...saw I the above post you looked at it....
    O2 sensors still origina??l....sometimes mpg can take a bit of a dive right before the front one turns on a light....
     
  10. Dave.0

    Dave.0 Helix & RMW Powered
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    I only get over 30 mpg driving down 81 south going to the Dragon with the cruise control on. Then I get about 400 miles a tank. * note that is all based off the cars computer which is wrong since I have a 15% pulley.

    Once I get to Fontana and hit the "FUN" roads I am lucky to see double digits sometimes. I swear I use more fuel and Meth at the Dragon week then I do all year.
     
  11. nismo4life

    nismo4life New Member

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    Well fwiw even after my 15% pulley the onboard computer has only been .5-1 mpg off on my car.

    The rear was changed at around 85k by Mini. The front was changed with an oem one before I picked it up because the CEL was on and it wouldn't pass emissions, that was at 127k.

    The car did through a P0138 O2 sensor circuit high voltage code. Only reason I ignored it is because this was at a time that it was throwing various codes over and over which ended up being the failed BPV. I haven't had anything in 2,000 miles since. Should I take them off and hit them with some brake clean you think? I'm going to be doing an OBX header soon anyway so it wouldn't cost me anything. I can also inspect the cat to make sure its not clogged or has anything stuff somewhere in it.
     
  12. cerenkov

    cerenkov New Member

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    What's the ethanol content in your fuel? Is it possible that you had been using ethanol free and now the stations are using 10% ethanol?

    This could explain 3-4mpg.
     
  13. nismo4life

    nismo4life New Member

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    Not likely. In CT its been 10% for a very very long time. I noticed in Maine the pumps also said 10%. I even scanned the car a few days ago for any possible pending codes and got nothing. I'm going to go ahead and order new tires, ebc red stuff for my JCW brakes and do that stuff see if it makes a difference. I don't smell/see any wear or excess dust on my wheels from the brakes, but I'm sure the tires aren't helping :crazy:.'


    Is there any way to check individual injector flow through some kind of very expensive specialist scan tool? I was planning on jumping over to JCW injectors sometime very soon. Is it possible I have one thats stuck open? Would the car still drive/function normally yet not throw a light?
     
  14. DixonL2

    DixonL2 New Member

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    The tires can EASILY be worth 10%+ in mileage, going to a really sticky wide tire from a more conservative one. Also note that (as said) a smaller diameter tire than stock will tell the car it's going more miles than it actually is, reducing indicated mileage.

    Also check your trans oil, refill with Redline MTL. That was worth 1.5MPG to mine, and the shifts are buttery smooth. Super easy job, on par with an oil change, but use a GOOD allen wrench and don't bugger up the threads.

    Check/replace your upstream oxygen sensor as well, or at least clean it. Made a diff on mine, more drive-able. They can start to "go" without throwing a code, only way to know is seeing the near-real-time "fuel trim" adjustments (of course on our cars the phrase "near real time" is a few times per second, not the dozens of times per second of the newer ones).
     
  15. ColinGreene

    ColinGreene Well-Known Member
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    could be all that drifting you do.
    or the huge ego your car has to carry.
    Probably the map sensors, Look for a vac leak.
     
  16. Firebro17

    Firebro17 Dazed, but not Confused
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    Gas mileage, what's that?
     
  17. ColinGreene

    ColinGreene Well-Known Member
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    dude Firebro! whats up!
     
  18. Firebro17

    Firebro17 Dazed, but not Confused
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    Hey Colin. Long time no drink!
     
  19. jamez

    jamez New Member

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    Zombie revival.

    I recently picked up a new-to-me 06 JCW that was getting an appalling 13L/100kms. It had an exhaust leak at the gasket mating the manifold/cat/downpipe and the exhaust.
    After the $10 gasket was replaced, it went back down to the more appropriate 10L/100kms with the same hard driving style (now easily achieving 5.6-7.3 L/100kms if being nice)
     

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