Let me start off by saying I'm only referring to premium unleaded and have not experimented with e85 mixing like some have. Everyone always has their tried and true favorite gas stations for filling, snacks, other things, but where do you go to fill up? Per the owners manual Audi recommends "top tier detergent gasoline" at least for the 3.0 tfsi and it just so happens this is the gas marathon stations sell. This is one of the most common and cheapest chains in my area so I always try and fill up here, especially since it seems to run better than cheaper premium. What are your thoughts? Do you think quality of gas has any effect on the carbon buildup issue some owners have experienced?

 

It sounds like you know this, but for those who do not, Top Tier fuel is different than octane level. Top Tier fuels must meet a certain quality standard, and pump prices tend to be more expensive than stations who sell fuel not certified as Top Tier.

I buy from my local Irving station, which was certified top tier but no longer is. I suspect it's the same fuel as before, but they don't want to pay for the certification.
Costco fuel used to be TopTier, but is not now in several locations. My wife fuels at Costco.

 

I ALSO buy from my local Irving station! Where are you from if you don't mind me asking?

 

Top-tier certification is based on the entire fuel chain/branded stations having to meet the standards for fuel storage/water controls/additives concentration meeting the standard, etc., etc. It's not something where some stations in a chain will get to 'opt-out', and in the case of Costco, I find that hard to fathom why they would move away from the top-tier fuel standard that they championed. I'd be asking questions.

"Costco is listed as a TOP TIER™ gasoline retailer. Find out more at www.toptiergas.com. Kirkland Signature™ Gasoline contains five times the EPA detergent requirement in both regular unleaded and premium grades, and is formulated to clean your engine and help your vehicle run like new."

To the OP; Yes, absolutely it matters if you buy fuel that doesn't have to meet any minimum quality standards; you're just getting whatever the terminal filled the truck up with, which is the base fuel that all stations use. The real difference is in the additives package and how much gets added, as well as water management and other factors that go into the top-tier fuel certification.

Lower fuel quality means less optimal combustion, so your engine is notably perkier and objectively gets better fuel efficiency running on top-tier fuel, be it gasoline or diesel, etc. The why is in oil contamination from blow-by gases, and the carbon-captured piston rings leading to dynamically increasnig oil consumption issues on the 3.0T engines, etc., etc. The problems begin with the diet you feed your Q7.

I have the Gas Buddy app on my phone and have it set to only show me stations with the top-tier fuel (use station filter in settings), so I don't even have to hunt for them. I also have realized that saving ten cents per gallon isn't actually saving me any money if I'm driving out of my way to reach that fuel station, so I don't wait to refuel if I'm below half tank and catch a deal on top-tier diesel at one of my preferred stations.

The other major factor is the fuel station's traffic, because you want a fuel station to be constantly turning over it's fuel supply rapidly, which means less chance of water contamination or storage tank related quality issues....freshly refined fuel is what you want, where possible.

Run a Q7 with generic fuel and it'll run perfectly fine, but then you fill it up with the top-tier fuel at the same octane level, and you will notice the difference, as will your engine, throttle pedal foot, and your backside G-meter, depending on how you drive it. You still need to be changing the oil at about half what Audi 'recommends' on the 3.0T engine if you want to avoid major issues down the line, and service all the driveline fluids Audi says are sealed/lifetime fluids requiring no maintenance.

Welcome to the world of Audi-isms and planned obsolescence.

 

Station in South Glastonbury, CT

 

I'm the guy that posted a couple weeks ago about my oil pressure light coming on after spring temps started, that problem still continues sometime but plan to remedy soon as I recently got my VCDS cable and found out it's an oil pressure sensor fouling up. I use liqui moly 5w-40 with a mann filter trying to keep the car as tip top shape as possible as I live in south-eastern Kentucky and the closest Audi dealer is 2 hours away lol. It just so happens the closest gas station to my house is a marathon station with the certification and it's .10¢ cheaper a gallon than everywhere else in town so I always try and fill up there. The car is our main mode of transportation so I've tried to do a couple tasteful mods suited to our location and get all the maintenance up to par since I bought the car used (I did get lucky however as the car only had 56k on it and was kept up to service standards at Audi stealerships its whole life per the Carfax). The car is due for new plugs and coils though so those are next on my list after a new battery

 

Related - Any recommendations on Fuel Additives (gas) for the items below (thank YOU) ?
a) Compensate for Winter Fuel mix in Northeast
b) Storage for ~30days