New (to me) S4, gas mileage is terrible

[Clintster]

Hey all, just quick background. I recently picked up a 2014 S4 and during the inspection the shop discovered an unknown tune with supercharger pulley. I still haven't been able to determine the brand of the tune, I've checked with 034, GIAC, and APR. It could be a home tune for all I know. Anyway, no idea how much HP it's pushing but the car pulls very hard. Using google maps I have figured out how many miles since I filled up with 93 octane on Friday afternoon.

Friday 31 miles
Saturday 0 miles
Sunday 20 miles
Monday 37 miles
Total 88 miles

My tank gauge is already below half. I'm worried I won't even be able to make it through a work week without filling the tank. I expected mileage to be lower than my previous car, but not this bad. Is it my tune? What kind of mileage are you all getting with a tune?

Clint

[Chris108]

I get between 20 to 22 mpg. Maybe a little less in the winter. My mileage wasn’t impacted at all when I went from stock to stage 1, then stage 2 EPL tunes. I’m fact it may have gotten slightly better.

As other have pointed out in the past, you can often determine which tune you have by reaching out to the major players and providing your VIN. Good luck with your new car.


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[zaxophne]

Do you use the computer to monitor your mileage while driving? How aggressive are you driving, do you do mostly city streets or freeway? Are your tires inflated properly. Do you need a carbon clean. What kind of gas are you using? Are you going up a lot of hills under acceleration?(I get 5MPG(or so) while going up a big hill here at full throttle)

[whts4]

I average 22mpg mixed urban driving, 29 mpg hwy on stock 2015, DSG Michelin AS/3 tires, BP premium fuel, driven in normal transmission and engine mode.

[BucDan]

Check your mileage at the pump. Reset your trip mileage first, fill up with gas, then drive until you need to fill up again. Once you fill up again, divide your mileage on the counter with the number of gallons you filled. That's the most accurate way to get a good MPG. I get around 22/23 when doing 30% city and 70% highway on stock. Medium high throttle until I can get to a good cruising speed with traffic.

[B5Dreaming]

Check your mileage at the pump. Reset your trip mileage first, fill up with gas, then drive until you need to fill up again. Once you fill up again, divide your mileage on the counter with the number of gallons you filled. That's the most accurate way to get a good MPG. I get around 22/23 when doing 30% city and 70% highway on stock. Medium high throttle until I can get to a good cruising speed with traffic.

The above is how you should be calculating your mpg. I think the computer doesn't do a great job, my trip mpg counter drops quickly while sitting at idle. As you've noticed the gas gauge moves from full to under half real quick, but then it will continue to move down at a much slower pace.

When I purchased the car stock I drove 1.4k miles home and got around 27mpg being very tame. Now I'm Stage 2 and probably average around 17mpg. Honestly, I blame the exhaust, the sound is addicting.

[Brother Owl]

Don't trust the car's MPG readout and log a longer distance of travel. I would recommend at least 3 or more tanks for a better estimate of your MPG.
Don't trust the car's fuel tank readout. 1/2 tank on the readout is nowhere near 1/2 tank, I've found that the car will have at least 2-3 gallons left when it's showing completely empty (14-15gallons to fill-up on E, 17 gallon tank).
Looking for possible ECU tunes - try contacting some of the other "smaller" tuners: IE, EPL, Unitronic, Revo, MRC, Malone.
Your ECU tune can cause lower MPGs than stock, but in most cases that's due to a heavier right foot. Most tunes will provide a small bump in fuel economy as the stock tunes runs rather rich.

[Clintster]

The above is how you should be calculating your mpg. I think the computer doesn't do a great job, my trip mpg counter drops quickly while sitting at idle. As you've noticed the gas gauge moves from full to under half real quick, but then it will continue to move down at a much slower pace.

When I purchased the car stock I drove 1.4k miles home and got around 27mpg being very tame. Now I'm Stage 2 and probably average around 17mpg. Honestly, I blame the exhaust, the sound is addicting.

Thank you both, I will be doing this for the next few fillups to see where i'm at.

[Clintster]

Do you use the computer to monitor your mileage while driving? How aggressive are you driving, do you do mostly city streets or freeway? Are your tires inflated properly. Do you need a carbon clean. What kind of gas are you using? Are you going up a lot of hills under acceleration?(I get 5MPG(or so) while going up a big hill here at full throttle)

I do use the computer but don't really trust it
I mean, I just got the car so i'm having some fun, but most of the time I drive pretty chill in comfort mode
Mixed city and freeway, probably 60% freeway
Need to check the tires
No idea if I need a carbon clean
Last fill was 93 octane from pacific pride (cardlock)
I have zipped up a long hill by my house a few times, it's hard not to.

[zaxophne]

I do use the computer but don't really trust it
I mean, I just got the car so i'm having some fun, but most of the time I drive pretty chill in comfort mode
Mixed city and freeway, probably 60% freeway
Need to check the tires
No idea if I need a carbon clean
Last fill was 93 octane from pacific pride (cardlock)
I have zipped up a long hill by my house a few times, it's hard not to.

I know the computer isn't going to give you great info but it's something you can look at while driving to get an idea.
Hills are super fun! I did some canyon carving when I first got mine and used half a tank(Maybe slightly less) in 20 minutes. Yep.

[Dr GP]

This car is really easy to drive fast.and not even know it.If you purchased this car and expected more than 18mph /city and 24 mph /highway,you are going to really be disappointment. City mileage is inversely proportionate to the amount of lead in your right foot Highway mileage is inversely proportionate to the speed you are driving. But not as sensitive as city driving

[Clintster]

This car is really easy to drive fast.and not even know it.If you purchased this car and expected more than 18mph /city and 24 mph /highway,you are going to really be disappointment. City mileage is inversely proportionate to the amount of lead in your right foot Highway mileage is inversely proportionate to the speed you are driving. But not as sensitive as city driving

I have significant lead in my foot at times, especially when a WRX or BMW is nearby...

[hunter_killer]

This car is really easy to drive fast.and not even know it.If you purchased this car and expected more than 18mph /city and 24 mph /highway,you are going to really be disappointment. City mileage is inversely proportionate to the amount of lead in your right foot Highway mileage is inversely proportionate to the speed you are driving. But not as sensitive as city driving

I was shocked when I got 36 mpg a few weeks ago with a mix of 30-31 mpg on a long trip. In town I usually get 22ish. Wasn’t bad for being fully loaded and driving in big hills/ grades.


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[Senseless]

Range for me is 14-26, city/highway. Untuned, but car has a lot of miles on it.

[MSq5]

Check with other tuners such as EPL and IE to see if the tune is theirs.

Check the simple things like air filter and spark plugs, both of which can seriously degrade gas mileage.

Have you driven the car enough to tell if it is using any oil or your coolant level is dropping?

Run a scan for codes. The best scan will be a deep scan by some sort of VAGCOM like Ross Tech VCDS. Those scans detect “soft codes” that don’t trigger a check engine light. Those codes identify failed or failing parts or systems that may account for poor mileage, such as the PCV valve.

[K_Estes]

I have significant lead in my foot at times, especially when a WRX or BMW is nearby...

don't we all.

[Dr GP]

I was shocked when I got 36 mpg a few weeks ago with a mix of 30-31 mpg on a long trip. In town I usually get 22ish. Wasn’t bad for being fully loaded and driving in big hills/ grades.


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At what speed? Not above 75mph, Down hill with the wind, slip streaming a tractor trailer

[oaybar007]

I have been averaging about 25-29mpg depending on how I drive the S4. Most of the time I'll just take it easy on acceleration and short shift in comfort mode, carry as much momentum off throttle as much as possible. Tire pressures are important, as is base operating condition of your equipment. If your car is up to spec then I'd suspect just conditional based on driving/climate situation and tune. If your car could benefit from maintenance like plugs, etc. then definitely try that. So many variables impact MPG that it's so hard to gauge though. I would keep digging on the tune because maybe there's room to iron that out there. Not entirely sure, but if your car is mechanically sound, then that's all that's really left.

[hunter_killer]

At what speed? Not above 75mph, Down hill with the wind, slip streaming a tractor trailer

72 roughly for an average speed. Never had a tail wind either. 112 miles divided by 3.1 gallons is a little over 36 mpg.


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[SteveYem]

IMO, 88 miles for half a tank is very bad and unusual based on your description of your driving habits, even if the car is tuned. I would suspect something bad in the ignition system (coil packs and/or spark plugs), or fuel system (bad fuel pump or bad injector). I don't think carbon crusted valves are going to make the car that inefficient. Do you have access to a Vag-com cable so you can check for misfires? Can you feel any cyclical, stumbling behavior from the engine when idling?

[ringtaxi]

17.8 in traffic only situations. Hwy closer to 22+. Stage 1 tune.

[B5Dreaming]

I filled up today. Got 16.7mpg for the tank. I've also been fairly aggressive since I'm new to Stage 2 and the shiny new toy feeling hasn't worn off yet.

Also decided to drop my tire psi from 39 around to 38 front / 36 rear to see if it drives any different.

[Glacier_S4]

I’m usually about 19 in Sport mode. Almost all city

[rpalmer]

They are not economy cars.

-RP

[Atrevido]

Stage 2 single pulley and I average 20.5 MPG with a 50/50 mix of highway and city driving. Definitely a "spirited" driver. I agree with everyone else who recommends
only using the gas pump to calculate the actual MPG. The car's built in computer tends to be a bit optimistic, to say the least.

[seandon_792]

This is my fuel averages and I’ve been stage 1 for all those miles. Currently at 123k miles, wouldn’t say it’s bad at all


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[Solo3]

This is my fuel averages and I’ve been stage 1 for all those miles. Currently at 123k miles, wouldn’t say it’s bad at all


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What app are you using? That looks pretty cool.

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[seandon_792]

What app are you using? That looks pretty cool.

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It’s called Fuelly. It’s free and works pretty well for tracking mileage and things like tire rotations or oil changes.


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[BEight SFour]

This is all freeway going 75-80 too. I think going 60-65 I would get 2mpg better every tripScreenshot_20200627-112204_Fuelio.jpeg

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[Clintster]

IMO, 88 miles for half a tank is very bad and unusual based on your description of your driving habits, even if the car is tuned. I would suspect something bad in the ignition system (coil packs and/or spark plugs), or fuel system (bad fuel pump or bad injector). I don't think carbon crusted valves are going to make the car that inefficient. Do you have access to a Vag-com cable so you can check for misfires? Can you feel any cyclical, stumbling behavior from the engine when idling?

Idle is a little rough IMO, but I can't tell if it's just a rough idle or misfire. Definitely driving habits have something to do with it, but i'm going to begin checking some things to make sure there are no other factors. When I had the car inspected they pulled codes and there was an ABS code and a door speaker code, that was it.

[MSq5]

Idle is a little rough IMO, but I can't tell if it's just a rough idle or misfire. Definitely driving habits have something to do with it, but i'm going to begin checking some things to make sure there are no other factors. When I had the car inspected they pulled codes and there was an ABS code and a door speaker code, that was it.

We are trying to suggest that you run a new full VAGCOM scan again and find a way to do a single gear (3rd) gear) at full throttle from 2,000 to redline and post the log or have someone look at it. I really want to know if you are having misfires and on what cylinders, if you are running rich, whether your fuel trims are normal, things that would shop up in a data log.

You may just need new correct heat range plugs properly gapped, or a new air filter, or may have one or more misfiring coil packs. We can’t really make any progress without you checking plugs and air filter and getting a scan done.

[dizzysn]

Calculating at the pump, I get about 14 if I drive having fun, 17 if I drive conservatively.

[Clintster]

We are trying to suggest that you run a new full VAGCOM scan again and find a way to do a single gear (3rd) gear) at full throttle from 2,000 to redline and post the log or have someone look at it. I really want to know if you are having misfires and on what cylinders, if you are running rich, whether your fuel trims are normal, things that would shop up in a data log.

You may just need new correct heat range plugs properly gapped, or a new air filter, or may have one or more misfiring coil packs. We can’t really make any progress without you checking plugs and air filter and getting a scan done.

Understood. I am planning on a dyno trip on Friday, I wonder if I could do it then? Never been to the dyno before so i'm not exactly sure what to expect, I just want to get some numbers to see where i'm at before I do any more mods.

[MSq5]

Understood. I am planning on a dyno trip on Friday, I wonder if I could do it then? Never been to the dyno before so i'm not exactly sure what to expect, I just want to get some numbers to see where i'm at before I do any more mods.

Honestly, you don’t use a Dyno for fixing bad things. You use it for optimizing what is good. Forgive me, but you seem to be getting the cart before the horse. At least you’ll get some AFR numbers, but really, please pull the plugs, inspect, change or regapped, check/clean/change the air filter. I know you are new to this, but a new full scan with VAGCOM and a data log will tell you a whole lot more. Geez, you know you have an aftermarket tune (different pulley) don’t know if you are on stock tune or an unknown aftermarket tune, and you are going to throw it on a dyno for multiple full power pulls?

If the dyno shop does tuning and has VAG specific equipment, maybe they can do the full scan and check basics like plugs before strapping it on the dyno. They might be able to do single gear data logging (not just boost and AFR) during the pulls.

Sorry for the tough love. I personally would not strap my car down for dyno pulls with known and unresolved performance issues. Where is all that fuel going? 88 miles on 1/2 tank of gas. No clouds of black smoke out the exhaust? I hope you don’t have an injector stuck or leaking or some other mechanical issue accounting for the really poor gas mileage. Oil contamination from gasoline? Does your oil smell like gasoline? Just please be careful.

[SteveYem]

Honestly, you don’t use a Dyno for fixing bad things. You use it for optimizing what is good. Forgive me, but you seem to be getting the cart before the horse. At least you’ll get some AFR numbers, but really, please pull the plugs, inspect, change or regapped, check/clean/change the air filter. I know you are new to this, but a new full scan with VAGCOM and a data log will tell you a whole lot more. Geez, you know you have an aftermarket tune (different pulley) don’t know if you are on stock tune or an unknown aftermarket tune, and you are going to throw it on a dyno for multiple full power pulls?

If the dyno shop does tuning and has VAG specific equipment, maybe they can do the full scan and check basics like plugs before strapping it on the dyno. They might be able to do single gear data logging (not just boost and AFR) during the pulls.

Sorry for the tough love. I personally would not strap my car down for dyno pulls with known and unresolved performance issues. Where is all that fuel going? 88 miles on 1/2 tank of gas. No clouds of black smoke out the exhaust? I hope you don’t have an injector stuck or leaking or some other mechanical issue accounting for the really poor gas mileage. Oil contamination from gasoline? Does your oil smell like gasoline? Just please be careful.

I think this is all good advice. I would not be running my car hard on the street, much less beating the hell out of it on the dyno, unless I was confident that it was performing reliably as a baseline. It sounds to me that this car needs a wellness check, including all of the fueling and ignition items that are mentioned above, before putting any undue stress on it. It's not a lot of fun, but less not-fun than causing a very expensive problem from running an unhealthy car too hard.

[Clintster]

Honestly, you don’t use a Dyno for fixing bad things. You use it for optimizing what is good. Forgive me, but you seem to be getting the cart before the horse. At least you’ll get some AFR numbers, but really, please pull the plugs, inspect, change or regapped, check/clean/change the air filter. I know you are new to this, but a new full scan with VAGCOM and a data log will tell you a whole lot more. Geez, you know you have an aftermarket tune (different pulley) don’t know if you are on stock tune or an unknown aftermarket tune, and you are going to throw it on a dyno for multiple full power pulls?

If the dyno shop does tuning and has VAG specific equipment, maybe they can do the full scan and check basics like plugs before strapping it on the dyno. They might be able to do single gear data logging (not just boost and AFR) during the pulls.

Sorry for the tough love. I personally would not strap my car down for dyno pulls with known and unresolved performance issues. Where is all that fuel going? 88 miles on 1/2 tank of gas. No clouds of black smoke out the exhaust? I hope you don’t have an injector stuck or leaking or some other mechanical issue accounting for the really poor gas mileage. Oil contamination from gasoline? Does your oil smell like gasoline? Just please be careful.

A little tough love never hurts. The dyno is booked out a month so I have some time and can cancel if necessary. I'm going to check the filter and probably replace with the aFe 10-10121, unless it already has one. I'm also going to pull the plugs and replace them. With 35k miles I assume it's never been done but I will inspect and get pics if anything looks funky. Also looking at the ross-tech VCDS Hex V2. I will "smell the oil" as well. I'm hoping that the car just has original air filter and plugs and replacing them will help fuel economy.

Clint

[BucDan]

A little tough love never hurts. The dyno is booked out a month so I have some time and can cancel if necessary. I'm going to check the filter and probably replace with the aFe 10-10121, unless it already has one. I'm also going to pull the plugs and replace them. With 35k miles I assume it's never been done but I will inspect and get pics if anything looks funky. Also looking at the ross-tech VCDS Hex V2. I will "smell the oil" as well. I'm hoping that the car just has original air filter and plugs and replacing them will help fuel economy.

Clint

Air filter will help if it's the original from factory, for certain, or hasn't been changed in 15K miles. Spark plugs, idk, it's far too early to replace them, but it doesn't hurt to look at them. I think factory timing for plugs is 60K miles/5 years? If so, I'd be interested to see what yours looks like.

[SteveYem]

Air filter will help if it's the original from factory, for certain, or hasn't been changed in 15K miles. Spark plugs, idk, it's far too early to replace them, but it doesn't hurt to look at them. I think factory timing for plugs is 60K miles/5 years? If so, I'd be interested to see what yours looks like.

True, but it's recommended to change plugs more frequently when tuned (I think??), and also I know at least EPL recommends gapping the plugs differently than the OEM spec. It's worth checking in any case.

[Clintster]

Air filter will help if it's the original from factory, for certain, or hasn't been changed in 15K miles. Spark plugs, idk, it's far too early to replace them, but it doesn't hurt to look at them. I think factory timing for plugs is 60K miles/5 years? If so, I'd be interested to see what yours looks like.

I'll have a new set of OEM NGK's tomorrow and let you know what mine look like. Maybe it's early but i'd rather be safe than sorry.

[BucDan]

I'll have a new set of OEM NGK's tomorrow and let you know what mine look like. Maybe it's early but i'd rather be safe than sorry.

Did you get the Iridium or Platinums? What's the torque spec for spark plugs, anyway?