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    Thread: Bad Fuel Economy.

    1. Member NotLowEnough's Avatar
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      04-28-2012 12:34 AM #36
      FWIW, Karl is Stg.1. Which strangely gets better economy than stock if driven right...
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    2. Member Blaylock1988's Avatar
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      04-28-2012 03:34 AM #37
      The reason why they are more efficient at lower end is because mechanical efficiency is the highest and your brake specific fuel consumption (horsepower/fuel ratio) is lowest. The lower the bsfc the less fuel it takes to get a certain amount of power. The method of fuel delivery might change combustion efficiency slightly (different mixing and turbulence in the cylinder) but it wont change mechanical efficiency at all, and combustion efficiency is already pretty high at low RPM too (above idle). So, gas mileage will always be worse at high RPM, which is an advantage of having a higher gear to shift into (overdrive).

      What direct injection does differently is controls the fuel more accurately in each cylinder. With indirect injection, fuel is often robbed by other cylinders, and fuel bounces up and down with the waves in the intake runners, so it is harder to get the correct amount of fuel inside the cylinder when the engine needs it. This means that direct injection gives better fuel delivery across the entire RPM range.
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    3. Senior Member feels_road's Avatar
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      04-28-2012 05:02 AM #38
      Quote Originally Posted by Dtullyjr View Post
      My Kumho all seasons are "extra load" tires and have quite the range from 35 PSI to 50 PSI max for reccomended pressure. Ive messed aroundwith the pressure a lot over the past couple months. Is there a tire pressure that is kind of universally known to be best for all tires? I dont know why the tires say extra load. Im assuming it means just that but I dont know what anybody with 17 inch tires needs extra load for. Im inclined to think my oem Continentals provided considerably better fuel economy, but I wasnt a fan of their grip and they didnt last long at all. Im open to suggestions here.....
      Yes, the rolling resistance of tires varies widely, and stickier tires typically (but not always) are worse; Conti Pro Contact for example are actually LLR (low rolling resistance). On the other hand, a better Conti all-season is the DWS, and a very good Conti summer tire is the DW. Tirerack may list rolling resistance so you can compare.

      As to tire pressure, many owners run somewhere between 38 and 40 - it doesn't really depend all that much on the tire, although Contis definitely like to be inflated. Under 38 you will slowly see a decrease in fuel economy and tire wear, faster at below 36, and below 33-34 both (and safety!) will go down the drain. Comfort goes the other way, of course.

      The only other thing I can think of is a regular (bi-weekly?) Italian tune-up. Has worked well in all of my cars, even at high mileage (>150,000 miles).

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      04-28-2012 08:54 AM #39
      Quote Originally Posted by Dtullyjr View Post
      I do have a heavy right foot when I drive and I really jump on the acceleration a lot. Does driving behavior like that really affect the car?
      The skinny thing on the right.. ya thats the Gas... the more its on the floor the more gas the motor consumes... witch explains the 25/28mpg hwy tops... take your foot out of it more and use cruse control when on the freeway ( more specific no more than maybe 5 over the limit) might contribute to getting 30+

      Quote Originally Posted by dstackmasta27 View Post
      All in all they get decent mileage, for the enjoyment of the auto. If I wanted better I'd be driving a base Civic or a Prius
      You mean TDI right?!?!?
      Last edited by blackout2006; 04-28-2012 at 09:02 AM.

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      04-28-2012 09:18 AM #40
      Quote Originally Posted by feels_road View Post
      The only other thing I can think of is a regular (bi-weekly?) Italian tune-up. Has worked well in all of my cars, even at high mileage (>150,000 miles).
      I've always heard of this process, but never knew it had an official name.

    6. Senior Member Aonarch's Avatar
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      04-28-2012 09:56 AM #41
      Italian tune up at least once a month, aka flog the car for a bit, do a few rolling 5-60mph 100% acceleration.

      Just a little bit though so you don't waste fuel.
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    7. Member Dtullyjr's Avatar
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      04-28-2012 10:48 AM #42
      I have found this to be very informative all so . The explanation of Direct Injections benefits was pretty fascinating and it reallymakes sense why more automakers are switching to this fueling setup. My tires are at about 38 psi now and now that I think of it, the Kumhos are stickier so that may explain some of it compaired to my old Conti's. Ill be trying to avoid overusing that "skinny black thing" to the right as well. Eh who am I kidding, as soon as I see 30 mpg on a trip Ill probably start blasting around again. The GTI is a gift and a curse

    8. Member rhodri45's Avatar
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      04-28-2012 11:14 AM #43
      Quote Originally Posted by Squirrel Nuts View Post
      This.

      I routinely get 30-32 mpg with the air on and 33-34+ with the air off and windows cracked. Best I ever got was 37.7.

      I get about 24-28 mpg in the city. Maybe I drive like a bitch.
      i must as well...
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    9. Member dstackmasta27's Avatar
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      04-28-2012 12:32 PM #44
      Quote Originally Posted by blackout2006 View Post
      You mean TDI right?!?!?
      ^literally this


    10. Senior Member feels_road's Avatar
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      04-28-2012 07:25 PM #45
      Quote Originally Posted by Aonarch View Post
      Italian tune up at least once a month, aka flog the car for a bit, do a few rolling 5-60mph 100% acceleration.

      Just a little bit though so you don't waste fuel.
      When I haven't had a chance to do a good hill-run here in a while, I usually do it on the freeway (empty, at night) after the car is warmed up, properly. For example, 3-4 runs from 50 mph to redline in third (TDI), full-go-pedal. Yesterday was such a night, I had warmed up the car 5 miles in the hills, showing 40 mpg then as indicated -- when I was home 5 miles later, it stilled showed 46 mpg.* Gotta love the TDI...

      * However, normally, in that direction, I get ~52-55 mpg. So, yeah - don't overdo it, otherwise it will cost you. On the flip side, in the TDI I see much better mileage for a week or so, because the DPF is nice and clean - so that compensates a bit.

    11. Senior Member Aonarch's Avatar
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      04-28-2012 09:54 PM #46
      Quote Originally Posted by feels_road View Post
      When I haven't had a chance to do a good hill-run here in a while, I usually do it on the freeway (empty, at night) after the car is warmed up, properly. For example, 3-4 runs from 50 mph to redline in third (TDI), full-go-pedal. Yesterday was such a night, I had warmed up the car 5 miles in the hills, showing 40 mpg then as indicated -- when I was home 5 miles later, it stilled showed 46 mpg.* Gotta love the TDI...

      * However, normally, in that direction, I get ~52-55 mpg. So, yeah - don't overdo it, otherwise it will cost you. On the flip side, in the TDI I see much better mileage for a week or so, because the DPF is nice and clean - so that compensates a bit.
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    12. Member Dtullyjr's Avatar
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      04-29-2012 12:36 AM #47
      I drove about two hours to and from to go mountain biking today. Lighter on the gas and driving a little smarter at 55-65 mph yeilded 31 mpg avg, Bike rack and all!

    13. Senior Member feels_road's Avatar
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      04-29-2012 12:56 AM #48

    14. Member DasMkVI's Avatar
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      04-30-2012 03:59 PM #49
      Quote Originally Posted by Dtullyjr View Post
      I was looking in the manual and couldnt find anything about air filter changes. Is that included in carefree maintenance? If not should I look into this as well? I may pull the plugs to inspect them. If I go that route, what torque specs do I use when reinstalling? Will I need to use a gap tool?
      Air filter is due every 60k on your car, which is pretty excessive if you ask me. I plan on changing mine at least every 30k. That is if I still have the stock airbox for that long!!! Your plugs should be fine but if it will make you feel better to pull them out to see if they're cocoa brown go ahead. The gap will remain the same unless you mess with it.

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      04-30-2012 04:18 PM #50
      Quote Originally Posted by Dtullyjr View Post
      Typically 71 mph is my cruising speed and that would get me about 33 back when it was new. Now tire pressure is a good question. My Kumho all seasons are "extra load" tires and have quite the range from 35 PSI to 50 PSI max for reccomended pressure. Ive messed aroundwith the pressure a lot over the past couple months. Is there a tire pressure that is kind of universally known to be best for all tires? I dont know why the tires say extra load. Im assuming it means just that but I dont know what anybody with 17 inch tires needs extra load for. Im inclined to think my oem Continentals provided considerably better fuel economy, but I wasnt a fan of their grip and they didnt last long at all. Im open to suggestions here.....
      I get about 30-31MPG when I drive about 72mph on the highway. But it varies a bit based on the terrain you drive on too, any kind of grade you will hurt that as well. Stage 1 tune in this case helps a little bit as I believe the engine runs leaner with tune, as factory calibration runs rich to protect against knock for differing fuel grade.

    16. Junior Member capitano_obvious's Avatar
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      04-30-2012 05:00 PM #51
      Quote Originally Posted by Squirrel Nuts View Post
      Guess I'm lucky I get such good mileage?


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    17. 04-30-2012 06:22 PM #52
      Quote Originally Posted by blackout2006 View Post
      The skinny thing on the right.. ya thats the Gas... the more its on the floor the more gas the motor consumes... witch explains the 25/28mpg hwy tops... take your foot out of it more and use cruse control when on the freeway ( more specific no more than maybe 5 over the limit) might contribute to getting 30+
      Actually, the more air the motor consumes. Unless you're driving a diesel, the skinny pedal controls airflow, not fuel flow. That's what O2 sensors and MAF's are for.
      Quote Originally Posted by TechEd View Post
      Long-story-short: Outie5000 is right on all accounts.

    18. Junior Member fatiredflyer's Avatar
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      04-30-2012 06:53 PM #53
      ...I bought four Humho 4x all season tires and had the dealer install them. The dealer asked if I wanted an alignment and I declined thinking it seemed ludicrous a new car would need an alignment. To be honest I was shocked I needed new tires already, but I did have a few backroad blasts that may have contributed to that...
      Pardon my newbiness (first post on VWV) but isn't it possible that a misalignment could be responsible for a sudden and noticeable decrease in mileage and a need for new shoes?
      A "few backroad blasts" could conceiveably have done the deed, and you've been paying the price since...

    19. Member SoCalMK6GTI's Avatar
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      04-30-2012 07:11 PM #54
      Quote Originally Posted by Outie5000 View Post
      Actually, the more air the motor consumes. Unless you're driving a diesel, the skinny pedal controls airflow, not fuel flow. That's what O2 sensors and MAF's are for.
      Well if you're gonna get technical and bring sensors into play, the skinny pedal on the right has a sensor which sends a signal to the Throttle Position Sensor at the Throttle Body which then tells the electronically controlled Throttle Body at what percentage of open/closed its supposed to be in, that percentage will determine your actual air intake flow at the TB.

    20. 04-30-2012 07:32 PM #55
      My last two tanks were 26.2 and 26.3



      If you do any measure of city driving, you're not going to get 30. I'd suggest you start keeping track on Fuelly (or similar) and see what you're really getting. I think, frankly, that where I am is pretty average.

      Take a look at this:
      http://www.fuelly.com/car/volkswagen/gti/2011
      http://www.fuelly.com/car/volkswagen/gti/2012
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      I am not your lawyer. This is not legal advice of any kind. I'm probably full of s-h-i-t anyway.

    21. Member iamgap's Avatar
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      05-05-2012 09:44 AM #56
      Quote Originally Posted by hoyalawyr View Post
      My last two tanks were 26.2 and 26.3



      If you do any measure of city driving, you're not going to get 30. I'd suggest you start keeping track on Fuelly (or similar) and see what you're really getting. I think, frankly, that where I am is pretty average.

      Take a look at this:
      http://www.fuelly.com/car/volkswagen/gti/2011
      http://www.fuelly.com/car/volkswagen/gti/2012
      There could be something wrong with the car, but it could also be the environment and driving style. I generally drive like a granny, until someone pisses me off. I hypermile. I put just enough pressure on the excellerator to increase speed, and the slushbox upshifts between 1800 and 2000 (depending on the gear).

      These are my last 5 tank averages.
      miles \ gal \ mpg
      418 \ 14.549 \ 28.73049694
      414.6 \ 13.853 \ 29.92853534
      407.5 \ 13.844 \ 29.43513435
      417 \ 13.459 \ 30.98298536
      441.2 \ 14.213 \ 31.0420038

      The low one included a couple of spirited drives down 9 mile road. The most recent includes an "Italian Tuneup". It will be interesting to see if I can maintain the higher average.

      On my "Italian Tuneup" I used manual mode 1st gear with moderate excelleration until redline, second to 45 MPH (the speedlimit) and then bumped up to 6th gear as fast as tiptronics would allow.


      gap

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      05-06-2012 09:31 AM #57
      As previously mentioned, if you're doing the 30k service soon, I'd have them replace the air filter. 60k mile rec'd filter change is way too many miles, IMO. Your tires/air pressure will greatly influence your mileage. Trade-offs.

    23. Member v-dubIV's Avatar
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      05-07-2012 11:43 AM #58
      Quote Originally Posted by Squirrel Nuts View Post
      This.

      I routinely get 30-32 mpg with the air on and 33-34+ with the air off and windows cracked. Best I ever got was 37.7.

      I get about 24-28 mpg in the city. Maybe I drive like a bitch.
      i usually get 31-33 highway and 26-28 city, check valves, plugs, dirty air filter, or look for a gas station thats ethonol free, and makes sure the car is fed a diet of 93
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