Help me with gas mileage

[CamrideA4]

My car gets the same gas mileage regardless of it I'm driving on the highway, or in the city or ragging on it. I consistently get between 280-320 miles to a tank every time and I can't figure out why. The only thing that I have found that is suspect is that my MAP is showing boost while cruising on the highway when my gauge reads 0psi. If I'm cruising on a flat section of the highway and are between 10in Hg and 0psi on the boost gauge I will show 1350-1500mbar on the MAP sensor in VCDS. I don't see 1010mbar (lowest reading) unless I let off the gas and see 15in Hg or more in the boost gauge.

I don't have any boost leaks, I've had a smoke test done. I pull 20in Hg at idle. Any other idea's of what may be going on? The MAP sensor reads perfectly fine under WOT and at idle it shows 1010mbar.

[jaychen]

500km out of a tank seems awesome if you're ringing its neck.

[CamrideA4]

500km out of a tank seems awesome if you're ringing its neck.

Well not constantly, but when I'm doing logging I'm doing a bunch of 3rd gear pulls and I'm usually driving pretty aggressively otherwise because I'm trying to beat on the tune. I might get closer to 250-260mi a tank like that. But normal mixed driving and pure highway driving result in the exact same mileage.

[walky_talky20]

Well on my 2001 I've been getting around 26 mpg consistently. About 80% highway travel with reasonably aggressive driving. When I first got the car it had a Tiptronic in it (!) and it got about 30mpg highway. The mileage went downhill even before I did the 5MT swap. I was hoping the swap would get me some mileage back, but not so much. Maybe 1 mpg. Anyway, this 26 mpg figure equates to about 390 miles per 15 gallon fillup. I can almost always get 400 miles out of the tank, but that's driving on "0" for at least 15 miles or so. Having vastly overestimated "0 miles" some time ago where I ran out of gas going up a hill, I tend to fill up at or before "0 miles" now. For the past 2 weeks or more I've been driving with the N75 unplugged, which gives only 3psi max. I thought this would vastly increase fuel economy, but it hasn't changed a bit! This is probably because I have to flog the living crap out the thing just to accelerate normally, lol. I also recently replaced the front (wideband) O2 sensor. No change there either. My MAF seems ok, but there is some kind of fueling issue going on as the instant trim really likes to go to +25% quite a bit under accel.

Your miles per tank would equal out to around 20-21 mpg or so, which is a little disappointing indeed. Have you logged the MAF recently? Or primary O2 sensor instant trim?

[CamrideA4]

Well on my 2001 I've been getting around 26 mpg consistently. About 80% highway travel with reasonably aggressive driving. When I first got the car it had a Tiptronic in it (!) and it got about 30mpg highway. The mileage went downhill even before I did the 5MT swap. I was hoping the swap would get me some mileage back, but not so much. Maybe 1 mpg. Anyway, this 26 mpg figure equates to about 390 miles per 15 gallon fillup. I can almost always get 400 miles out of the tank, but that's driving on "0" for at least 15 miles or so. Having vastly overestimated "0 miles" some time ago where I ran out of gas going up a hill, I tend to fill up at or before "0 miles" now. For the past 2 weeks or more I've been driving with the N75 unplugged, which gives only 3psi max. I thought this would vastly increase fuel economy, but it hasn't changed a bit! This is probably because I have to flog the living crap out the thing just to accelerate normally, lol. I also recently replaced the front (wideband) O2 sensor. No change there either. My MAF seems ok, but there is some kind of fueling issue going on as the instant trim really likes to go to +25% quite a bit under accel.

Your miles per tank would equal out to around 20-21 mpg or so, which is a little disappointing indeed. Have you logged the MAF recently? Or primary O2 sensor instant trim?

MAF is new and is reading correctly, it gets logged all the time while I'm working with Malone to tweak my tune. Primary O2 sensor is also new (~4 months) and I log fuel deltas all the time as well. No idea how to tell if those are accurate, but I did get an OEM O2 sensor, not a universal.

I should mention I've had this issue almost as long as I've had the car. It used to be a little better and I'd get maybe 25mpg on the highway, but I don't think I've ever gotten 400 miles out of a tank even on highway only tanks. I always attributed it to being turbo and AWD, but that's obviously not it.

[Stubek]

My car gets the same gas mileage regardless of it I'm driving on the highway, or in the city or ragging on it. I consistently get between 280-320 miles to a tank every time and I can't figure out why.

You do realize the range you gave of 280 to 320 miles per tank is about a 13% difference between low and high. Also, with frankenturbo and the green giants, you probably won't get better than that.

[CamrideA4]

You do realize the range you gave of 280 to 320 miles per tank is about a 13% difference between low and high. Also, with frankenturbo and the green giants, you probably won't get better than that.

The FT and green giants shouldn't matter cruising on the highway out of boost as long as the tune is right. That's why I mentioned the weird MAP issue, as it looks to me that the ECU is seeing the engine under boost while cruising (when my gauge tells me there is no boost).

And yes that's a 13% spread, between 18-21mpg, which is shitty. I should be getting better than 21mpg on the highway. I'm running a K04 size turbo, not a BT.

[Seerlah]

When was the last time you changed your fuel filter? Also, short drives consume more gas (sub 10 min drives) along with hard braking instead of coasting to a stop. Tire pressure?

[CamrideA4]

When was the last time you changed your fuel filter? Also, short drives consume more gas (sub 10 min drives) along with hard braking instead of coasting to a stop. Tire pressure?

Fuel filter was changed when I installed the FT in January, so about 15k miles ago. Most of my driving to work is 25-35 minutes, and my tire pressure is 35psi. I do coast and don't brake hard. I've done everything short of hypermiling to try to get my mileage up.

[Seerlah]

Even though you stated you replaced these parts, but signs point towards the primary o2 sensor and MAF (more towards primary o2 sensor. it's just because it is the usual culprit). Maybe try different spark plugs. The 2.0 ignition coils and larger gap should grant you better gas mileage. If you were planning that upgrade, maybe try that out first. And FWIW, IE has the adapters for cheaper (distributer I know has the adapters and coil packs for $153 before shipping). Not hating on INA (great products), but obviously try to save some coin where I can.

[CamrideA4]

I'm already running the 2.0 coils and I'm gapped at .035.

Sent from my DROIDX

[Seerlah]

Gap them wider

[walky_talky20]

I am running 2.0T coils at .043 and didn't notice any fuel economy gains either. Sad Panda.

[Seerlah]

^Oh really? Then what's the only real benefit? Better combustion?

[CamrideA4]

I've got about 10k miles on these plugs so I'll swap in some new ones and gap them at .040. I don't see that making much difference though.

No comment on the weird MAP readings while cruising? Has anyone else logged their MAP sensor at constant load on the highway?

Sent from my DROIDX

[flynnr]

you should try ti not drive hard at all for one full tank (believe me this is nearly impossible, but worth it if you actually succeed)

I have a BT and have no problem getting 30mpg when cruising hwy... if anything, a bigger turbo would mean you are in boost later in the rpm, so you can stay out of boost easier, therefore get better gas mileage.

[CamrideA4]

you should try ti not drive hard at all for one full tank (believe me this is nearly impossible, but worth it if you actually succeed)

I have a BT and have no problem getting 30mpg when cruising hwy... if anything, a bigger turbo would mean you are in boost later in the rpm, so you can stay out of boost easier, therefore get better gas mileage.

I have, its the same. I've had a tank that was 99% highway cruising at 70mph and I got 320 miles out of the tank. This is why I bring up the map discrepancy, because my ecu is showing 5-7psi of boost when I'm cruising and my gauge shows 0psi.

Sent from my DROIDX

[-:vw:-]

The FT and green giants shouldn't matter cruising on the highway out of boost as long as the tune is right.

Keep telling yourself that ;) Check that o2 sensor, fill tires closer to the MAX rating, don't down shift or engine brake, shift at 3k or less religiously, check your plugs to make sure that fuel is burning efficiently, lots of little things especially driving habits are huge contributors. It will take time for you to see the benefits of changing up your driving habits. It will not happen over night or on one tank of gas.

[paulorama]

All of you seem to be getting great mileage. My stock 1.8tqm avant gets 19-20 city and 21-24 freeway. I don't know what the problem is. I get 280miles mixed (mostly city) driving in Portland. 240ish miles in San Francisco and 340ish max miles on the freeway with an empty car

[csosnowski]

^ sounds like me =( cant figure out the weird gas mileage.

[SS92]

Same here. 20-21 highway, 18 city. Sucks man. Just a quick thread jack, the 2.0 coil packs seerleah and walky mentioned... Any modification to ignition harness needed? I need a colder plug and my plugs right now look like crap. I need new coil packs as it is, so thinking of doing this + bigger gapped plugs might help me out a little. Have an ATW.

I get like 280 to a tank. Changed up driving habits a bit, don't spool unless I need to and shift at 3100 and I gained about 20 to a tank, pending how many ricers pull up next to me lol.

[csosnowski]

I have the 2.0t coilpacks on my 2000, no changes just regap your plugs and toss em on. They did improve, slightly, the mileage but not as dramatically as I had hoped. I think there is still something wrong and I havent had time to dig in and find it lol.

[walky_talky20]

For an ATW there are no modifications needed. Just the coil packs and the "coil pack adapters". Check the B6 forum for the huge thread on the INA adapters. The coils plug right in, although some have "refreshed" their ignition harness and have reported noticeable gains with that (ie: "cripser" response and smoother idle, not so much mpg's). I have a new harness to install someday as well. It's in my ever-growing pile of parts that I have been collecting. I need to get with the freaking program and bolt some crap to my car already.

[SS92]

Is it the harness from ECS that was half price or something crazy low? I thought it was an AEB harness I saw. Don't have the $$ to spend on a new harness, but I know mine is cracked to hell and back. I need one haha.

sorry for the thread jack op, and thanks walky. I'll go look for the thread. I was in it one of the days a while ago when it first started, havent checked since.

[cory.smith]

Keep telling yourself that ;) Check that o2 sensor, fill tires closer to the MAX rating, don't down shift or engine brake, shift at 3k or less religiously, check your plugs to make sure that fuel is burning efficiently, lots of little things especially driving habits are huge contributors. It will take time for you to see the benefits of changing up your driving habits. It will not happen over night or on one tank of gas.

Werd.

Did a comparison. Left the car in the care of an adult middle aged school teacher for one summer while I was on the west coast.

My mileage is better than she averaged over 3 months by a whopping 2mpg.

Just by the difference in driver.

-Cory

[CamrideA4]

FWIW the adapters are a visual mod, they're not needed to hold them in place (at least on an AWM engine). I've been running the 2.0T coils without adapters for ~6 months and no problems, they've never popped out.

And I know driving habits are not causing my fuel mileage issues. I've driven on plenty of tanks staying out of boost, it doesn't make much of a difference. When I replaced my O2 sensor a few months ago I immediately went on a trip and got exactly the same mileage. That was 300 miles of no boost cruising on the highway at 70-75mph.

[Seerlah]

Bad pcv valve?

[CamrideA4]

Bad pcv valve?

Just replaced that and the rubber piece that comes off the crank case and ties into it about 3 weeks ago, had no bearing on gas mileage. SAI is deleted as well, I haven't done the whole vac line cleanup yet though (but I don't have any vac leaks, 20 in Hg at idle).

[walky_talky20]

Is it the harness from ECS that was half price or something crazy low? I thought it was an AEB harness I saw. Don't have the $$ to spend on a new harness, but I know mine is cracked to hell and back. I need one haha.

sorry for the thread jack op, and thanks walky. I'll go look for the thread. I was in it one of the days a while ago when it first started, havent checked since.

It was this harness, which is no longer on sale:
http://www.ecstuning.com/Flyer-Sprin...ance/ES477951/

I think I payed like $18 for it (yes an entire engine harness for $18 - the dealer tech would not let me go until I gave him details). I was going to do a writeup on how I used that Jetta 2.5 harness to replace mine, but seeing as they are no longer available, I don't think it is applicable anymore. The next best price would be a Jetta 1.8T OEM replacement harness for around $50.

[mysman]

Agree on the O2 sensor, but disagree on avoiding engine braking, because that's when you're in fuel cut-off, at least on my AEB, and it's a big mileage booster around town. Try engine braking up to a red light and watch you instantaneous mileage hit the 200mpg limit. As far as upshifting, the best rpm for max mileage is right around the torque peak, about 1800 rpm for me, but the FT may be a bit higher. I usually get 400-450 miles per tank, and have gotten significantly higher by following these rules religiously, and consistently pissing off a lot of cars behind me, lol. BTW, mine is a 1.8T manual FWD Passat with APR stage ECU. The quattro tank capacity is slightly different. Also the tire circumference can vary the odometer as much as 5%, ie, worn out is better for "mileage" than new, or the difference in plus sizing vs. OEM. The total wheel weight (rotational inertia) can vary mileage (and performance) significantly.

[Black_97 A4]

I switched my oil to Mobil 1 0w-30 fuel economy or something like that and my mileage went from 26mpg-29mpg consistent mix of high way and local driving.

[CamrideA4]

Can anyone do me a huge favor and log their MAP sensor while cruising on the highway? I'd love to know if something is off there and if I should buy a new MAP sensor or not.

Sent from my DROIDX

[CamrideA4]

Can anyone do me a huge favor and log their MAP sensor while cruising on the highway? I'd love to know if something is off there and if I should buy a new MAP sensor or not.

Sent from my DROIDX

Anyone? I'll paypal someone $10 to do it (on a properly running K03/K04 car). I just need VCDS logs of your actual boost while cruising at around 65-75mph on a flat section of highway (throttle input should be nice and level).

[Seerlah]

I would, but I think I have a WG issue. I can boost maybe 17psi max on the hwy and maybe 13psi max city driving. My tune is written for 21psi. I can still do it if you want?

[CamrideA4]

I would, but I think I have a WG issue. I can boost maybe 17psi max on the hwy and maybe 13psi max city driving. My tune is written for 21psi. If you want, I can still do it if you want?

If your gauge shows 0psi or less while you're cruising it should be fine. I just want to compare what the ecu reads at 0psi while cruising to what the boost gauge is reading.

[Seerlah]

I'll try to post it before the end of the night. Need to go out anyways to the next city over.

PS: Don't need the $10