Glock.-

Hey all, I'm a new poster who owns a 2017 Audi A4 Ultra. I purchased the car in summer of 2017, and initially it was absolute perfection. I used to get 30 MPG city and 50 MPG highway *easily*, and acceleration was linear and predictable. I know the Ultra is not a very powerful car but for the most part it drove like a sports sedan.

However, fast forward a few months and I'm starting to notice poor performance and mileage. What used to be 30-50 MPG is now 20-40 on a good day. Acceleration feels hesitant and underpowered, and many times pressing the gas pedal results in the MPG gauge dropping like a rock but barely any hint of acceleration. It almost feels like the car has endless turbo lag and never boosts.

Does anyone have a clue what could be causing this issue? My first (uninformed) instinct is to blame the turbocharger or fuel injection system, but I'm interested to see what you guys think. I'm not eager to take it to the dealership without an informed opinion, as they tend to dismiss issues and take forever diagnosing problems.

The car is rolling on the stock Continental tires slightly overinflated to 40 PSI. It's only ever used 93 octane gas (the best we have here in the Northeast) save for the time my mom visited and filled it up with 87 octane. It's just had the complimentary service done, the one before the first 10,000 mile/1 year service interval.

minmet

" It's only ever used 93 octane gas (the best we have here in the Northeast) save for the time my mom visited and filled it up with 87 octane. " Just one time with 87 octane right? Shouldn't affect that much.
Since you are in NE, If I were you, I would dump a bottle of HEET Gas-Line Antifreeze & Water Romover to give it a quick try in case you have water get in there and iced up the fuel line. It does happen in cold days in NE.
Also, I wouldn't hesitate taking the car to the dealer.

uberwgn

Glock, I'll assume you are in the USA and we're talking US gallons. The official ratings for fuel economy from AUDI USA are:

Obsidian3K

I would also add that it's winter, and lower fuel economy is to be expected. I've been tracking fuel economy on my cars for over a decade now, and every year like clockwork, there's a 10-15% increase in fuel consumption that coincides exactly with sustained sub-freezing temperatures, and that fades away once spring hits.

Given your numbers that's probably not the whole story, but I'd bet that it's a substantial portion.

Glock.-

Huh straight into the fuel tank? I've noticed the issue occurring on warmer days as well, do you think this product would help?

Glock.-

Yeah of course, I'm a bit **** about efficiency and keep a spreadsheet of both the computer's reported mileage and my calculated mileage, derived by dividing the distance driven by the gas I put in the tank at the next fill up. I'm sure there's some variance between pumps, but the error should not be very large. Every time I fill up, I zero out the odometer, short, and long term calculators and start again.

I've noticed my calculated MPG is always higher than the computer's calculated mileage by 1-3 MPG. For example, I once took a 6 hour road trip with my friend and our luggage and logged a computer calculated 48 MPG average for the entire trip, but according to the pump/odometer I did a hair over 50 MPG. Unfortunately with my current mileage trends my commute will only net me 20-25 MPG.

I've asked the dealer about this issue and they cast some vague blame on the winter blend of gas which actually does line up with the timing of my problem - do you really think it's worth going in for a dedicated checkup? My dealer has turnaround times of forever and sometimes doesn't even fix the problem (took three appointments to fix the door rattle).

Thanks for the help.

Glock.-

Yeah the dealer actually blamed the winter blend of gasoline for my power and efficiency woes, and it does line up with when I started experiencing these issues. I guess I'll have to keep an eye on the problem until spring, perhaps this 2.0 Miller cycle engine is more sensitive to fuel composition than normal engines.

Fantasiamon

OP-

Are you using brand name 93 Octane? If you're using discount 93 that could also be a potential issue contributor. Maybe?

R8ready

Tires plays a big part. Make sure they are running at what they are recommended to be running at

bob m

If I were in charge of this forum, I would not let anyone become a member and post here without including a location in their signature area. Having a location facilitates a more accurate response. Having said that, I find 50 mpg absolutely impossible to achieve in the 2.0 A4. Somethings wrong here.