2.0T Degradation of Fuel Economy (165K miles)

[in4mation]

Hi guys, I bought my 2011 A4 2.0T Quattro as a CPO back in 2013 with ~15k miles. I work from home but spend many hours on the highway visiting clients in other states; as a result, she now has ~165k on the clock. The 2.0T reliably provided 31-32 MPG for many of those miles but I've noticed a slow decline in resulting MPG and now I'm lucky to achieve 26-27 mpg. I recently installed what might be its 3rd set of Continental Extremecontact DWS 06 tires, so tire compound/brand shouldn't have an effect. The car runs great, smooth idle and regularly serviced at the dealer. As a matter of fact, I just had it in for service for an oil change and diagnostics to ensure there were no codes in the computer that hadn't illuminated a light in the dash. Dealer said everything looks good on the computer, including the turbo.

My initial thought was dirty injectors however based on my research, I'm leaning towards an O2 sensor. I'd rather not play the "lets replace parts till it goes away" game, so I figured it was worth a shot to start here because I know many of you have cars with +100K miles, so I can't be the only one experiencing a car that runs great and looks good on a computer but is starting to have a healthy appetite for fuel!!

Many thanks in advance.

[09SCiduA]

Check your plugs, clean your intake charge pipes and throttle body...Hmmm, winter fuels tend to make less efficiency...however, I'm not certain if that's regional or not...up in the north, winter fuels reduce MPGs by 10-15%+...just spit-balling ideas...I'd check the plugs as that's easiest...

[Audibot]

My fuel economy dropped from when I changed my Pilot Sport A/S 3+s to Pilot Sport All Season 4s. Quite possibly the tires

[in4mation]

Hi 09SCiduA,

NGK Plugs and OEM Audi coils are new (<5k miles). I hadn't thought about cleaning the throttle body or the added effects of winter fuel, which I am certain is distributed in PA this time of year. I've done a bit more research on changing the O2 sensor and at this point, I think it makes sense to change it, even if it's not the culprit. There is a good chance all three could be contributing to the overall reduction I'm experiencing. Thanks for sharing your thoughts and ideas!

[jjvwg]

Ever done a carbon cleaning? That should definitely help you out a bit. If you can find someone local to you with VCDS, have a look at your fuel trims and see if anything looks wonky as well.


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[in4mation]

jjvwg,

I have not. Guessing a local speed shop might be a good place to start? I don't know if my local Audi dealer offers the service and likely charges a fortune if they do!

[scsu]

jjvwg,

I have not. Guessing a local speed shop might be a good place to start? I don't know if my local Audi dealer offers the service and likely charges a fortune if they do!

For a local independent check out Nothing Leaves Stock in Coopersburg. They do top notch work and, despite the name, do routine maintenance and repairs.

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[JWebb_C7_Comp]

For a local independent check out Nothing Leaves Stock in Coopersburg. They do top notch work and, despite the name, do routine maintenance and repairs.

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Air filter, plugs, coils. Listed in order of increasing cost. Also, this seems silly, but see if tire pressure is set lower than before. A couple lbs can mean a loss of mileage. Also, higher ethanol content in fuel and mean a loss in mileage though the Ethanol can allow for more timing advance and power if tuned.


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[in4mation]

Hey thanks scsu! Coopersburg is only a ~30 min drive for me!

[rcprato]

If you haven’t done a carbon cleaning of the valves and intake you should have that done or at least scoped to see what it looks like


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[JLAllroad]

165k miles on the clock, have you done a timing service?

What are your OCI’s?

As others have said
Air filter
I’ll add clean the MAF sensor when you do the throttle body.
Fresh plugs and coils

Personally I feel that injectors, hpfp, and pcv become suspect beyond 100k, some may say the same about O2 sensors and the catalyst can become clogged if consuming oil.

Tire pressure, wheel bearings (notorious on Audi) and yes alignment.

Lastly good gas, top tier, if you don’t know look it up, and yes winter Ethanol content, upwards of 15% vs 8-10%, will affect mileage.

Now I didn’t bring up carbon cleaning valves because many don’t notice a pre/post difference, but others have solved issues by doing it. Personally, I would say do it once every 100k and or when switching out injectors.


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[sincmaster27]

Add a can of BG 44k PLATINUM to the gas, also try shell 93 gas, you may also want to change the fuel pump and filter in the tank.


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[RPMtech147]

I've never seen a B8ish(A4-5-6) 2.0T quattro get better than around 24mpg mixed driving, including my own. I work on a lot, and sometimes check the average the MPG on them, just too see.

I have seen over 30mpg "indicated" on long road trips on my personal car, but like I said, day to day, 24mpg, mixed highway and city.

Now my A3, with the earlier 2.0T, that thing easily does 30mpg, but it's a FWD/manual and weighs quite a bit less.

[19birel]

So I have a '13 B8.5 A4 (CAEB engine) with this issue as well. Around town the economy is a little low but not super out of the ordinary, but on the highway it gets 22mpg driving quickly and 24-25ish if I'm careful. When I got the car it would get 32mpg on the highway If I was careful and driving "at pace" would put me around 27mpg.

My car has 117k miles though this started a good while ago, and it's maintenance history is pretty comprehensive. oil ever 5k miles, Plugs every 15k miles, R8 coils installed ~75k miles and replaced (preventative) at 115k with APR coils, freshly cleaned BMC air filter, carbon cleaning @95k miles, PCV ~97k miles, n75 ~100k, full timing service ~105k miles.

Not saying those items aren't your problem but I didn't really notice a change knocking those items off my maintenance list over the past couple years. My next play was going to be fuel filter, followed by injectors but the O2 sensor another member mentioned could be a good place to start. I have a used spare floating around my garage so I'll swap it out and report back with my findings

[MyDimeIsUp]

I'd be interested to see what an O2 sensor swap does. I feel like maybe I may be in for an O2 sensor too because I'll get a P0420 within 100 miles of driving, clear it, then go 1,500 miles until P0420 is triggered, clear it, then get it two more times in driving 400 miles.

[JLAllroad]

So I have a '13 B8.5 A4 (CAEB engine) with this issue as well. Around town the economy is a little low but not super out of the ordinary, but on the highway it gets 22mpg driving quickly and 24-25ish if I'm careful. When I got the car it would get 32mpg on the highway If I was careful and driving "at pace" would put me around 27mpg.

My car has 117k miles though this started a good while ago, and it's maintenance history is pretty comprehensive. oil ever 5k miles, Plugs every 15k miles, R8 coils installed ~75k miles and replaced (preventative) at 115k with APR coils, freshly cleaned BMC air filter, carbon cleaning @95k miles, PCV ~97k miles, n75 ~100k, full timing service ~105k miles.

Not saying those items aren't your problem but I didn't really notice a change knocking those items off my maintenance list over the past couple years. My next play was going to be fuel filter, followed by injectors but the O2 sensor another member mentioned could be a good place to start. I have a used spare floating around my garage so I'll swap it out and report back with my findings

Your BMS pedal tuner, IE tune/JB4 will significantly alter your data.

That said APR stg2 will be 20-22mpg city and 28 shorter highway, can hit 30-32mpg if I choose not to pass going WOT and keep it under 80. Gas mileage increases significantly below 75-78mph.

A few notes,

It takes some time to heat up the transmission and gear oils, more so in the winter, this takes a toll on short trips (under 20 miles?)

I recently ran stock for a bit, city was 22-25, and I was in high 20’s on mixed drives.

What I can say, WOT on these can go through some fuel, tuned or not, with a pedal tuners you’re probably WOT well before the end of the travel.


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[in4mation]

@RPMtech147: My 2011 used to return about the same, 22-24 MPG for mixed driving. +80% of the vehicle's miles are for trips that average 6-10 hrs. Flat interstates yielded ~30-32 MPG @75-80mph; mountains yielded ~27-29MPG. I had no complains at those speeds!

[19birel]

Your BMS pedal tuner, IE tune/JB4 will significantly alter your data.

That said APR stg2 will be 20-22mpg city and 28 shorter highway, can hit 30-32mpg if I choose not to pass going WOT and keep it under 80. Gas mileage increases significantly below 75-78mph.

A few notes,

It takes some time to heat up the transmission and gear oils, more so in the winter, this takes a toll on short trips (under 20 miles?)

I recently ran stock for a bit, city was 22-25, and I was in high 20’s on mixed drives.

What I can say, WOT on these can go through some fuel, tuned or not, with a pedal tuners you’re probably WOT well before the end of the travel.


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I had a period of JB4+pedal tuner where I got decent fuel economy, but I have changed the settings of both so many times they're definitely a variable. I have the pedal tuner on my other car as well (a 7.5 GTI EA888.3 2.0T), and no reduction in fuel economy there but the settings on it might be much tamer.

Could definitely be a contributor, but this issue seems to have effected a number of these cars so I'm not sure it's the entire cause. My economy around town is a little low, but explainable entirely by my lead foot, I would anticipate (and this is just hypothesis) that if JB4 and Pedal Tuner were the primary culprits my city economy would be hot trash and the highway economy more palatable by comparison.

Either way, I'll experiment with those to rule them out and start digging from there!

[in4mation]

JLAllroad:

My 2.0 was rebuilt (sorta), under Audi's infamous piston ring recall at around 125K. They also replaced the timing chain tensioner but to my knowledge, did not replace the timing chain. I suppose the answer to your first question is: I don't know. and I'm embarrassed to say I don't know what the acronym (OCI's) stands for. I have replaced the air filter, plugs, and coils in the past 6k-7k miles. New tires and alignment performed within the past 1,500 miles and I typically run ~38-40PSI in all 4 tires.

You bring up an interesting thought about the cats, which ingested many quarts of oil until consumption was sufficient for Audi to consider for replacement under the recall (1 qt. @ 500 miles) I do use namebrand gas and run the occasional can of injector cleaner but I'll be honest, I'm not sure I'm using the best kind. I'm going to take your advice about the MAF and throttle body cleaning.

As for carbon cleaning, do you think it's possible for a chemical in the fuel or run through the air plenum to do the job, or am I limited to finding someone who will blast it with walnut shells?

[JLAllroad]

JLAllroad:

My 2.0 was rebuilt (sorta), under Audi's infamous piston ring recall at around 125K. They also replaced the timing chain tensioner but to my knowledge, did not replace the timing chain. I suppose the answer to your first question is: I don't know. and I'm embarrassed to say I don't know what the acronym (OCI's) stands for. I have replaced the air filter, plugs, and coils in the past 6k-7k miles. New tires and alignment performed within the past 1,500 miles and I typically run ~38-40PSI in all 4 tires.

You bring up an interesting thought about the cats, which ingested many quarts of oil until consumption was sufficient for Audi to consider for replacement under the recall (1 qt. @ 500 miles) I do use namebrand gas and run the occasional can of injector cleaner but I'll be honest, I'm not sure I'm using the best kind. I'm going to take your advice about the MAF and throttle body cleaning.

As for carbon cleaning, do you think it's possible for a chemical in the fuel or run through the air plenum to do the job, or am I limited to finding someone who will blast it with walnut shells?

Log cam phase adjustment, if it’s over 5% you’re in need of a timing service.

OCI=oil change interval, Audi specifies 10k, that’s part of the piston ring issue (among potentially others caused by this interval), suggest 5ish.

If you run top tier fuel (google it) you won’t need injector cleaner, but, because it’s a direct injection engine it won’t help with the valves, nor will any other chemical, once they’re coated they need to be scraped or blasted.


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[MyDimeIsUp]

JLAllroad:

My 2.0 was rebuilt (sorta), under Audi's infamous piston ring recall at around 125K. They also replaced the timing chain tensioner but to my knowledge, did not replace the timing chain. I suppose the answer to your first question is: I don't know. and I'm embarrassed to say I don't know what the acronym (OCI's) stands for. I have replaced the air filter, plugs, and coils in the past 6k-7k miles. New tires and alignment performed within the past 1,500 miles and I typically run ~38-40PSI in all 4 tires.

You bring up an interesting thought about the cats, which ingested many quarts of oil until consumption was sufficient for Audi to consider for replacement under the recall (1 qt. @ 500 miles) I do use namebrand gas and run the occasional can of injector cleaner but I'll be honest, I'm not sure I'm using the best kind. I'm going to take your advice about the MAF and throttle body cleaning.

As for carbon cleaning, do you think it's possible for a chemical in the fuel or run through the air plenum to do the job, or am I limited to finding someone who will blast it with walnut shells?

Using some BG products on the intake valves and scraping manually with some copper bristle brushes works pretty well. Since BG doesn't sell directly to the public, you can just buy some "BG Air Intake, Valve & Combustion Chamber Cleaner" from eBay and do it yourself. Walnut blasting will be the best option to make it looking sparkly and pretty but if you want to do it yourself you need to buy walnut shells, an adapter for our intake ports for your pressure hose and vacuum, and also a container to store the walnut shells. Usually costs you ~$300 in parts. With some BG, remove the intake manifold and pour the BG product ontop of the valves (make sure the valves are completely closed for that specific cylinder). Let it set and eat away at the carbon, scrape with copper bristle brush, then suck out with baster and dry with compressed air and/or towels. A little elbow grease you'll be about 95% of the way there of walnut blasting for about 1/6th the price.

[MongoMcG]

This is a good point about cost (unless you have further use for the media blaster tank or plan to sell it after the gig). There are quite a few threads and videos about the process - both chemical and walnut shell blasting. I did the walnut shell thing, but after 136,000 miles the valves still required a little bit of scraping with picks to clean the toughest chunks.

Here is my post about the walnut shell experience: https://www.audizine.com/forum/showt...1#post14772528
Once the required tools were acquired (media blaster tank, wand, valve cleaning attachment for shop-vac, and walnut shells, the whole process was complete in just under two hours.

And a couple of vids that show the processes for chemical and media blasting:





This is a BMW, but you get the idea. There are a couple of companies that make the attachment for the shop-vac to use on the Audi 2.0T:

[mrg_B8TFSi]

Without going through entire thread so I apologize if my comments have been said already.. but given those direct injection platforms on the TFSI I’d likely start with the following list to try to regain the fuel economy you had:
* run only ethanol free fuel at 90 octane or better, if you can’t find ethanol free in your area than run premium 93 and add some injection cleaner in for awhile, seafoam in the fuel like a can per tank
* sounds like gummy valves and at 165k I’m sure you could do with a media blasting (walnut blasting) on your valves to restore a little more compression to squeeze out as much power per explosion as you can
* likely not injectors, my experience is they either work fine or they don’t work at all
* plugs might be wrong heat range or gapped wrong
* oil breather assembly (PCV) probably needs replaced, this regulates intake vacuum
* turbo wastegate linkage probably has some slop in it, not enough to create underboost faults but enough to diminish some power. Could check that as well as all the pipes on the intercooler and intake
* air intake partial obstruction, air filter and related pathways
* HPFP this failure will typically create a rich fault when it’s going bad but it could be worn out along with the cam follower where it’s not getting to the fuel pressure the ECM was programmed to run, and ECM is compensating with extended injector durations- long shot but I’ve seen it, and High fuel pressure sensor on fuel rail need to confirm that is correct reading as it doesn’t throw a fault
* maybe slightly weak oil pressure making motor work a tad harder, you mentioned routine dealer services but this motor is very sensitive to oil that isnt spec’d correctly
* water pump module, if you are not getting motor up to operating temp you will have poor fuel efficiency.. typically these WP assemblies leak and go bad causing overheating but stuck open thermostat would cause a cold motor condition and if you are not leaking coolant at 165k assuming original WP than that would be amazing and probably a record

Just a few notorious issues to consider


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[MyDimeIsUp]

if you are not leaking coolant at 165k assuming original WP than that would be amazing and probably a record

I'm running original water pump with no problems at around 159k miles. I guess some get lucky some don't. For 2 1/2 years since I got the car I've been waiting for it to leak but nothing

[mrg_B8TFSi]

I'm running original water pump with no problems at around 159k miles. I guess some get lucky some don't. For 2 1/2 years since I got the car I've been waiting for it to leak but nothing

Wow that’s awesome!!! I just hit 90k on mine but i preemptively put a new pump in at 80k on the basis of all reports indicating it’s weak points and service lifespan.. it wasn’t leaking at all and in fact the seals and bearings are prefect it’s still a good pump. Yep some were built on a Wednesday while a lot were built on a Friday night, same with the oil consumption motors , I have no issues with mine, original pistons with the first oil control upgrade and it doesn’t burn a drop. But 159k is a great out of your pump..


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[in4mation]

UPDATE 3/5/23 I started my latest milk run from Louisville, KY back to Allentown PA (~640 miles) with a few minor changes from earlier trips. The best part of this test is that I'm traveling the exact same roads and I stop at the same gas stations every time. So what did I change on this trip: I bumped tire pressures from 38 to 42 PSI and ran a big can of Royal Purple Max Clean fuel system cleaner because it was highly recommended by a few people, including at least one or two of you on this forum. Having used a number of fuel injector cleaners over the years, my confidence in a product costing 4x more remained low. To my surprise, my fuel consumption gradually increased to the point the trip computer reported an average of 30.7 mpg by the time I pulled off the highway. I also noticed smoother acceleration on the hills of WV and mountains in PA. The improvement makes me want to clean the valves to see how much more could be realized!

So what did I learn? Small adjustments in tire pressure might mean more than you think and a cheap fuel injector cleaner is equivalent to tossing dollar bills out the window as you drive down the highway and of course, all of you are AWESOME!!! I can't thank each and every one of you enough for your help and support. I'll post an update with any further work and improvements in performance.

[JLAllroad]

UPDATE 3/5/23 I started my latest milk run from Louisville, KY back to Allentown PA (~640 miles) with a few minor changes from earlier trips. The best part of this test is that I'm traveling the exact same roads and I stop at the same gas stations every time. So what did I change on this trip: I bumped tire pressures from 38 to 42 PSI and ran a big can of Royal Purple Max Clean fuel system cleaner because it was highly recommended by a few people, including at least one or two of you on this forum. Having used a number of fuel injector cleaners over the years, my confidence in a product costing 4x more remained low. To my surprise, my fuel consumption gradually increased to the point the trip computer reported an average of 30.7 mpg by the time I pulled off the highway. I also noticed smoother acceleration on the hills of WV and mountains in PA. The improvement makes me want to clean the valves to see how much more could be realized!

So what did I learn? Small adjustments in tire pressure might mean more than you think and a cheap fuel injector cleaner is equivalent to tossing dollar bills out the window as you drive down the highway and of course, all of you are AWESOME!!! I can't thank each and every one of you enough for your help and support. I'll post an update with any further work and improvements in performance.

I would be more concerned about tire wear and comfort at 38-42psi, both are quite high


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[mrg_B8TFSi]

UPDATE 3/5/23 I started my latest milk run from Louisville, KY back to Allentown PA (~640 miles) with a few minor changes from earlier trips. The best part of this test is that I'm traveling the exact same roads and I stop at the same gas stations every time. So what did I change on this trip: I bumped tire pressures from 38 to 42 PSI and ran a big can of Royal Purple Max Clean fuel system cleaner because it was highly recommended by a few people, including at least one or two of you on this forum. Having used a number of fuel injector cleaners over the years, my confidence in a product costing 4x more remained low. To my surprise, my fuel consumption gradually increased to the point the trip computer reported an average of 30.7 mpg by the time I pulled off the highway. I also noticed smoother acceleration on the hills of WV and mountains in PA. The improvement makes me want to clean the valves to see how much more could be realized!

So what did I learn? Small adjustments in tire pressure might mean more than you think and a cheap fuel injector cleaner is equivalent to tossing dollar bills out the window as you drive down the highway and of course, all of you are AWESOME!!! I can't thank each and every one of you enough for your help and support. I'll post an update with any further work and improvements in performance.

Glad you’re running well and back to expected fuel consumption… did you run better octane or better fuel? It is interesting that Audi does have in their literature top tier fuel vendors that should be used in the B8 platform.. and obviously not everyone that owns an Audi are likely in an area that supports the 10 or so top tier gas stations.. but a trip like that is a great way to get the injectors clean and possibly burn out some carbon


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[in4mation]

I would be more concerned about tire wear and comfort at 38-42psi, both are quite high


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Ironically, I noticed very little difference in ride quality on the factory 19” wheels. I did lower air pressure from 42 to 38 psi on our return trip to Indiana (Aka: milk run from PA to KY = ~650 miles). Slight decrease in MPG but still managed a respectable 29 mpg.

As for tire wear, I’ve logged ~150k miles on a few sets of Conti Extremecontact DWS and regardless of how many times I’ve had this car aligned by Audi, it wears out every set of tires as if it has a mild negative camber issue (normal?); plenty of tread remaining in the center of the tires. So I’m purposely running this set of tires at a higher pressure in hopes of realizing more even tread wear. Time will tell if it was a dumb idea. IMG_2428.jpg