Horrable Gas Millage "19mpg"

[gotboost]

Ever since I got mt car Ive been getting right around 19 mpg. Its a 2003 a4 1.8t Quattro, with 61k miles. I just replaced the air filter at 60k, Ive run sea foam through the intake manifold, and fuel cleaner in the gas tank multiple times. Really dont know what else to do, any ideas because I know I should be getting way better gas millage. Thanks

[Kerschera4]

check your tire pressure
change your fuel filter
lay off the gas some

[gotboost]

check your tire pressure
change your fuel filter
lay off the gas some

Tire pressure is 32psi all around... Yeah I was gonna change the fuel filter next. Were is the cheapest place to get one? And I drive like a grandma, so I know it isnt from beating on the car

[1point8teeNW]

Primary O2 sensor is shittin the bed. Happened to me around the same mileage. I'm still running on the junk one and I'm at 108k now.

Lemme guess. You're spending 60 a week in gas and only going about 250 miles on that tank?

[gotboost]

Primary O2 sensor is shittin the bed. Happened to me around the same mileage. I'm still running on the junk one and I'm at 108k now.

Lemme guess. You're spending 60 a week in gas and only going about 250 miles on that tank?

Yep 60 a week and about 260-280 miles and fil up 14.3-14.8 gallons....


anyway to be 100% sure that its the primary 02 sensor

[tuner culture]

Could be that you are running -APR Stage 1+/ TT 225 Injectors (takes more gas)

[jessefrank]

Make sure you don't have any boost leaks, etc. Do you have a CEL or any other codes? One other idea is to check your injector o-rings, if your injector seats look wet or have alot of dirt build up they may be bad.

[gotboost]

^^^ I was getting the same millage before APR 1+, that didnt change on bit, It doesnt seem like i have any boost leaks, boost gauge holds 11 psi at redline and there is no leak around the injector o ring, just got the injectors in a month ago.

[jm121189]

How much boost does it hold between 3k-5krpm? 11psi at redline seems a little low even for a ko3.

[gq9]

Could be that you are running -APR Stage 1+/ TT 225 Injectors (takes more gas)

Wrong. I'm Revo stage 2, and bigger injectors. I get more than 350 to a tank.

[younga4]

do you have access to vag com?

I simply replaced my oxygen sensors and coolant temp sensors before I received any warning codes, all is good for now.

coalesce

[ehfour]

Are you Tip or 5 spd?

What kind of driving do you do?

19Mpg in the City with a Tip w/heavy 19"s sounds about right?

[A4 in SC]

19Mpg in the City with a Tip w/heavy 19"s sounds about right?

I have to say, I didn't expect my mileage to be as low as 19-21 in the city with a tip! Very disappointed, as I routinely had 26-28 in my previous B5 5 speed. Depended on how hard I drove it. I drive my tip like a grandpa and still only get 19-21. SUCKS!

Where's the best place to get the 02 sensor? I'm going to assume the primary is BEFORE the cat?

Thanks,
Mike

[Dolphin18T]

boost gauge holds 11 psi at redline and there is no leak around the injector o ring, just got the injectors in a month ago.

11 psi is low for 1+. You should be spiking around 20-21 and holding ~19.

[jessefrank]

11 psi is low for 1+. You should be spiking around 20-21 and holding ~19.

^^^that's what I was thinking; not much difference between major software companies.

I'm REVO stage 2, but had to have the stage 2 file de-tuned (per REVO spec's) due to not having a full exhaust/TP (and an IC wouldn't hurt).

So since GotBoost dosen't have the 1+ (stg 2) upgrades listed in his sig that are usually recomended to get full potential (aka boost) from the 1+ file...I'm not sure how much boost he'd be running. I don't have a boost gauge, so can't really help much there. 11PSI still seems too low though.

[Mike02A4]

I get around 20mpg with all local stop and go driving. I drive the car easy as well. Mines a 5 speed manual and stock. Its got a brand new Audi catalytic converter.

[aaaudiprotein]

Primary O2 sensor is shittin the bed. Happened to me around the same mileage. I'm still running on the junk one and I'm at 108k now.

Lemme guess. You're spending 60 a week in gas and only going about 250 miles on that tank?

I'm in the same boat.

[7speed]

dont feel to bad, I only get 300 miles to a tank and Im Revo Stage 3 w/440cc. I thought my gas milege sucked.

How can you tell if your 02's are fouled ? I don't have any codes

[gotboost]

My boost spikes at 20 psi holds about 17 then goes down to 11psi, and also I do have a 5spd....so is there anyway to tell if the o2 is 100% toast

[gotboost]

Are you Tip or 5 spd?

What kind of driving do you do?

19Mpg in the City with a Tip w/heavy 19"s sounds about right?

Mostly drive on the highway, 5spd and i was getting the same milage with my stock 17's

[diztek]

im stage 2 giac quattro, and i do all city driving with about 30% lead foot action. im getting around 250-260 a tank as well. i did notice a big improvement when i did my fuel filter, probably getting about 15 to 20 miles more per tank.

[texasboy21]

wheres the fuel filter located?? Is it an easy swap??

barrett

[doublezero30]

Yep 60 a week and about 260-280 miles and fil up 14.3-14.8 gallons....

exactly what im getting with exactly the MPG i was getting. i uped it to 21mpg by cruising in 4th at 40 rather than 3rd . i know i need to do my fuel filter soon. changing my sparkplugs soon too. just put a new airfilter on...really dont want to do an o2 sensor if that is whats causing the problem. them thangs iz expensive yo.

wheres the fuel filter located?? Is it an easy swap??

barrett

its right next to the fuel tank i believe on the passanger side. its relatively easy. easier if you have a lift...but i mean, what isnt?

[absolutegtr]

Primary is the first O2 sensor...the one BEFORE the cat.

[LateApex]

Driving at lower rpms (what i think some of you meant by staying off the gas) does NOT save you gas...driving between max engine efficiency and power output does (somewhere around 3000-4000 rpm). Just ease on the gas so you dont get a turbo+fuel spike then shift normally at around 4k or so. Engine braking helps as well and keeps you within the power rpms. You may want to go as far as to downsize from your 19" rims to some lighter 17's that require less travel when you're just commuting. When you upsize that much you can really screw up the gearing unless you have some serious low-pros. I regularly get at least 28-34mpg around town driving like this on my completely stock car (for now hehe...parts on the way). For some of you this stuff is obvious but for many it is not. Hopefully this helps someone.

[diztek]

just filled up. from a full tank i got 189 miles and i had a little over a quarter tank left.

[A4 in SC]

You may want to go as far as to downsize from your 19" rims to some lighter 17's that require less travel when you're just commuting. When you upsize that much you can really screw up the gearing unless you have some serious low-pros.

Sorry, but that's simply not true. When going +1, +2, or more, if done correctly, you maintain the overall diameter. While increasing the wheel diameter, you should decrease the sidewall height accordingly (decreasing the tire's aspect ratio).

There are many online calculators to help determine the correct tire size when going +1, +2, etc. However, the formula is:

tire width x aspect ratio / 25.4 (changing from metric to inches) x 2 (two sidewalls per overall diameter) + (wheel diameter) = overall diameter

225/45/17 = 24.972"

225 x .45 /25.4 x 2 + 17 = 24.97"

Same goes for 225/40/18:

225 x .40 /25.4 x 2 + 18 = 25.086"

As you can see, the overall diameter didn't change very much at all. (.11")

What DOES affect your gas mileage with larger diameter wheels is the added overall unsprung weight.

With all of that said, it looks like I'll be doing a fuel filter (I remember it being a PITA in my B5), both oxygen sensors and plugs soon.

Mike

[haroulli]

This is a good topic,

I'm fairly disappointed with my gas milage! I have stock 03 A4 1.8T Quattro Tip with sports package and 73k. I do a fair bit of driving around town in traffic and I always try and manually shift. I get around 300 - 325 miles before the gas light comes on. I always figured all our cars are like that as we have the quattro and the tip. I check my tire PSI regularly and I only fill up with 93. Should i be getting more MPG in the city? When i drive highway I usually get around 350 - 360 before the light comes on.

[a4darkness]

I'm wondering if my car is suffering from the same problem. Recently, the mpg seems to be falling off. Just replaced the fuel filter about two months ago as well.

[LateApex]

"What DOES affect your gas mileage with larger diameter wheels is the added overall unsprung weight."



I know all that and if you read what you quoted then you would see that I said you must need 'seriously low profile tires'...Also 'if done correctly' upsizing your rims and therefore replacing rubber with lightweight metal should actually DECREASE unsprung weight which is the opposite of what you said if I read correctly. Possible problems I suggested before are A) your rims are probably not lightweight and therefore there is no reason at all (in terms of efficiency) to have them and B) You are increasing your spring rate by decreasing the tire wall which is not always a good thing in excess (for performance). Since I did not know the size of your tire and you seem to be incapable of getting reasonable mpg I think suggesting lighter and smaller wheels would be perfectly reasonable. Good luck with your fuel filter replacement anyway as it can't hurt.

[LateApex]

Also, I have a 6m so your tip's (if you have 'em) are probably the problem. I've never driven an a4 with a tip but I'm guessing that they're less efficient.

[A4 in SC]

"What DOES affect your gas mileage with larger diameter wheels is the added overall unsprung weight."



I know all that and if you read what you quoted then you would see that I said you must need 'seriously low profile tires'...Also 'if done correctly' upsizing your rims and therefore replacing rubber with lightweight metal should actually DECREASE unsprung weight which is the opposite of what you said if I read correctly. Possible problems I suggested before are A) your rims are probably not lightweight and therefore there is no reason at all (in terms of efficiency) to have them and B) You are increasing your spring rate by decreasing the tire wall which is not always a good thing in excess (for performance). Since I did not know the size of your tire and you seem to be incapable of getting reasonable mpg I think suggesting lighter and smaller wheels would be perfectly reasonable. Good luck with your fuel filter replacement anyway as it can't hurt.

Not sure why you're confused, as larger diameter wheels with the appropriate sized tires WILL weigh more than smaller diameter wheels with the appropriate sized tires. So no, you didn't misunderstand what I said. A plus sized wheel/tire combo WILL WEIGH MORE that the same wheel/tire combo in a smaller size (keeping the same overall diameter). I don't get your whole replacing rubber with 'lightweight metal' reasoning. Again, simply not true.

Case in point -

BBS CH wheels and Good Year F1 GS D3 tires (weights taken from tirerack.com)

22 lbs. (17x8.5) + 25 lbs. (235/45/17) = 47 lbs.
26.1 lbs. (19x8.5) + 24 lbs. (235/35/19) = 50.1 lbs.

With a larger wheel/tire combo, you will NOT increase the overall diameter and you WILL increase your unsprung weight at each corner. Sorry if you don't get what I'm saying.

From your original post:

You may want to go as far as to downsize from your 19" rims to some lighter 17's that require less travel when you're just commuting. When you upsize that much you can really screw up the gearing unless you have some serious low-pros.

Am I misunderstanding what you said? I read that you were saying that having a plus sized wheel and tire will increase your overall diameter? If you purchase the correct sized wheels and tires, you will maintain the SAME overall diameter. What do you mean by 'screw up the gearing'? Again, if you purchase the correct plus sized wheels and tires, you will maintain the same overall diameter, and 'the gearing' - I'm assuming you mean speedometer gearing? - will no be effected.

Yep, I have a tip, and I realize my mileage won't be as good. Probably in the neighborhood of 2-3 mpg compared to a comparable car with a manual transmission.

[surreal]

what is your vacuum at idle? I searched for a little over a month for why my gas went to hell was getting 19-20mpg. replaced front o2 new intercooler lines nothing. Turns out my forge dv was crap. put a vacuum pump on your dv and see how much vacuum you can pump and hold on it don't go over 20. if it holds its ok if it doesn't like mine did replace it. I'm back up to 28-30 again. hope this helps.

[A4 in SC]

Hmm, this will be and easy one for me, as I have a new TT225 DV (can't remember the part no.) in the garage that I had bought for my previous B5. I'll have to try that first. Obviously, any change in mileage will help!

[DELUX]

Tire pressure is 32psi all around... Yeah I was gonna change the fuel filter next. Were is the cheapest place to get one? And I drive like a grandma, so I know it isnt from beating on the car

32 psi!? My tire pressure is 42psi all around, lol. You should fix that first. Then after that, it's all your driving.

If I'm heavy on the gas for a tank, I'll get between 18-20mpg. But I've taught myself to cruise less aggressively and pick and choose when I open up the throttle. I never take it over 3500rpm under regular driving, you shouldn't either if you wanna have good mpg. I get between 25-27mpg (50/50 city/highway) with my new techniques. Long highway hauls still bring me ~28-30mpg.

Fix your tire pressure and after that the answer is in your foot.

[mxrz]

Also 'if done correctly' upsizing your rims and therefore replacing rubber with lightweight metal should actually DECREASE unsprung weight

Unsprung weight... We're talking about wheels, not control arms or brake calipers. Wheels rotate if you didn't know, and even if a drum of a 17" wheel is statically heavier than a drum of a 19" wheel, the latter becomes heavier, in simple terms, when it starts spinning at normal speeds. This effect is compounded by the low profile tires, as they also concentrate more mass closer to the edges (shorter, stiffer sidewall is heavier per surface area, compared to a taller more flexible sidewall).

[1point8teeNW]

Just because your primary o2 sensor is going out doesn't exactly mean there will be a CEL. I've been ridin around on a junk one for awhile now and I'll only get a CEL maybe once every four months. I'll clear the code, then continue. If I figured the amound of extra gas I use VS the amound of gas I'd save with the new sensor....I could've paid for a new sensor for everyone in this thread.

[darkstar]

my 19's do effect my gas milage i get about 20 more miles per tank with my 16's on! after i did my fuel filter, and oil change i gained like 80 more miles per tank!

[old guy]

my 19's do effect my gas milage i get about 20 more miles per tank with my 16's on! after i did my fuel filter, and oil change i gained like 80 more miles per tank!

I'm not surprised. Even if your 19's (tire and wheel together) weighed the exact same as your 16's (tire and wheel together) you would get better mileage with the 16's. The reason is because the 16's have a lower "Moment of inertia". Simply stated, as you move the weight out further from the mid line the force required to accelerate or decelerate the rotation of an object (in this case your wheel and tire assembly) increases. As the force increases your mileage decreases.

[HeymyAudi]

im getting on a bad day 24.5mpg and thats dogging it.. and Im a Giac +1 and 19's .....