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    Thread: how much do spark plugs affect fuel consumption?

    1. 01-30-2003 11:58 AM #1
      i'm barely getting 300 miles per tank and have noticed a few others with much better results. i was wondering if it might be related to the plugs and the gaps. i was getting multiple engine misfires when the car was only a few months old. techs told me it was no problem. after reading a few archived posts about plugs and their job, i was wondering if maybe my stockies aren't gapped correctly or something.

      BTW, only mods are suspension and DV.


    2. 01-30-2003 12:04 PM #2
      I'm curious about this too. My last tank yielded 250 miles. I suppose it could be the cold weather, but that seems really low (about 19 miles a gallon).

    3. 01-30-2003 01:57 PM #3
      It all depends on your driving. Two drivers on the same car can yield 200 or 400 miles per full tank

    4. Banned Kilmer's Avatar
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      01-30-2003 02:07 PM #4
      quote:
      It all depends on your driving. Two drivers on the same car can yield 200 or 400 miles per full tank

      maybe so, but I doubt it...I saw my fuel consumption go down after it started getting really cold here in PA...and then I babied the car and still got the same milage...I think it's the cold somehow...maybe I should change my spark plugs and wires???


    5. 01-30-2003 02:13 PM #5
      for me, whether it's cold or hot, nothing over 300 mpt if i'm lucky! something has got to be wrong. i have a heavy foot, i'll admit but even when i take it easy i only squeeze a few (10 or so) more miles out.

    6. Member jcstomper's Avatar
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      01-30-2003 02:17 PM #6
      quote:
      It all depends on your driving. Two drivers on the same car can yield 200 or 400 miles per full tank

      maybe so, but I doubt it...I saw my fuel consumption go down after it started getting really cold here in PA...and then I babied the car and still got the same milage...I think it's the cold somehow...maybe I should change my spark plugs and wires???



      yeah its the cold, i just had a loaner 2.slow for 2 weeks and still got crappy gas milage with that.

    7. Banned Kilmer's Avatar
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      01-30-2003 02:22 PM #7
      I had a 2k Golf before this car...and I always stomped on it...even though it dint' go anywhere...well I beat on it and got pretty much the same gas milage...with this car...before the new year...I was getting 350 to a tank now 275-300 if babied.... ...I was under the impression that I would get 28-32 mpg...I guess I was wrong...

    8. 01-30-2003 03:57 PM #8
      thanks for all the replies but i don't think any have actually answered me yet. is it worth it for me to check in to my spark plugs as being a possible culprit?

    9. Member jcstomper's Avatar
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      01-30-2003 04:21 PM #9
      oh whoops sorry bout that, yeah check for gappage and fouling, maybe run a bottle of redline fuel injector cleaner for safe measure

    10. Member droopy1592's Avatar
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      01-30-2003 04:26 PM #10
      GAS MILEAGE is always crappy in the winter. It's the gas mix, man!

      If you got too many miles on those plugs, you probably need to change them anyway.

      It's been said that good wires and plugs can give you 5-10% gas mileage and mo' power, but I haven't proven it to be true or seen independent test.


      [Modified by droopy1592, 9:30 PM 1-30-2003]

      In many ways then this car is like herpes. Great fun catching it but not so much fun living with it every day. - Jeremy Clarkson

    11. 01-31-2003 02:20 PM #11
      quote:
      thanks for all the replies but i don't think any have actually answered me yet. is it worth it for me to check in to my spark plugs as being a possible culprit?

      How many miles do you have on those? If it's more than 25K, it could be a good idea. I changed mine after 25K miles and got better performance, but I don't remember if my MPG improved or not?


    12. 01-31-2003 02:25 PM #12
      just over 10k on the clock. btw... my MPG are the same whether it's cold or hot, driving conservatively or gunning it. i'm not asking about replacing them so much. i'm just thinking that maybe they're not gapped identically to each other. i remember reading a thread not too long ago where someone measured the gap on all four plugs and found four different measurements. will the size of the gap affect my MPG?


      [Modified by spooled_rave, 11:26 AM 1-31-2003]

    13. 01-31-2003 06:57 PM #13
      When's your next schedueled service? When you go in, ask them to check the Spark plugs and also change the oil to Synthetic (if you haven't done that yet). Synthetic alone improves fuel efficiency around 5%. All above said, I don't really think there's anything wrong with your car and it could be bad Winter gas or something like that. Normally, you should not change spark plugs until at least 25K (serviec manual recommendation is much longer).

    14. Member LaFerrari's Avatar
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      01-31-2003 07:37 PM #14
      After 35k miles I changed my plugs to the cheap autolites just to see if they were any better. I still get the same kind of acceleration but my fuel consumption has risen dramatically. My driving habits haven't changed at all but I get approx 6mpg less than before the plug change. I haven't pulled them to check the gap but I will this weekend when I change the oil. I also use BG 44k every 3k miles.
      Quote Originally Posted by GTI2Slow View Post
      If there is enough room to shoehorn a car seat in the back by the roll cage I think this might be the car to buy.

    15. 01-31-2003 08:58 PM #15
      Definately pull a couple of plugs and see if they are fouled and if the gapping is off. If they look fine and gap is right, then you don't need to replace them. If they are not alright then I bet you will get better gas milage. BTW everyone during the winter gets horrible gas milage due to winter gas and timing being more advanced due to the tempature. I usually get 300 on my car, lucky if I get 230 right now.

      Also, are cars don't have wires, you can only replace the plug.


    16. Member Alpha-3's Avatar
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      02-01-2003 09:08 AM #16
      I see you have an '02 1.8T. It could be the plugs, but because of a carbon buildup. That's what happened to me. I could easily get 360-400 miles per tank, and that's even opening it up on the FLA turnpike; even around town, I don't break the law but I drive 'spirited'. Mileage dropped off some, seems it is all part of the coilpack thing too. Mine misfired in the mornings for a few minutes until she warmed up; had one bad coil replaced.

      A month or two later had it in to the dealer for its 20k check and told them about the cold start thing, misfiring hadn't gone away. They replaced the ECU; also said the intakes valves had carbon buildup; I had to leave the car all day because the dealer said they were going to clean the valves and change the plugs as well. That seemed to do the trick. It's back to almost 380 to the tank now.




      [Modified by SLVR BLT, 9:09 AM 2-1-2003]

      2014 CSG GTI

    17. 02-01-2003 09:32 AM #17
      The condition of the plugs will affect gas mileage, but if you see your mileage start to drop considerably, I'd be suspect of the O2 sensor(s). In general you want to run the widest gap you can without causing the car to miss. I've had to gap the plugs in my last boosted cars down due to the spark being blown out under big boost.

      If you are running colder than needed plugs, they tend to lose their ability to self-clean, and fouled plugs will have a negative impact on MPG.

      And to echo what was stated above, the MTBE mixed in to our 'winter fuel' will also have a negative impact on MPG.



      [Modified by johnAWD, 7:58 AM 2-1-2003]


    18. Member LaFerrari's Avatar
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      02-01-2003 11:30 AM #18
      My poor fuel consumption started the day I installed new plugs, so I doubt the o2 sensor is to blame.
      Quote Originally Posted by GTI2Slow View Post
      If there is enough room to shoehorn a car seat in the back by the roll cage I think this might be the car to buy.

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