mrassoul45

I recently bought a 2012 Audi A4, I wanted to know from the community if using premium fuel is a hardline rule or is there any play with using a lower (< 91) octane. Interested to know everyone's feedback.

jagtoes

Less octane is less power and less mileage. It will run on it but the difference isn't worth it.

D'AudiA47

Yeah this confused me when I first got my A4 since I was so used to regular unleaded from my old Nissan Altima, and apparently this one can take a at least two types of fuel Premium or Super. I started out only using Plus fuel since that was the highest one that i'd see, and then some stations i'd go to would only have Super. Now i've just gotten accustomed to only using Super for the last few months so lets hope I don't screw anything up haha.

SMac770

Use the octane documented on the fuel flap. More is a waste of money, less will reduce performance and might harm the engine. As usual, there might be more to the story than fits on some little door, so review your owner's manual.
Not sure what octane you're referencing with the terms plus, premium, and super. The words are ambiguous. "Super" 95 RON in Europe = "Premium" 91 AKI in US. Gasoline is just gasoline, with different octane ratings. The RON vs AKI numbering schemes do not denote different fuels per se.
The Audi 2.0T is designed for Premium to achieve the advertised power and economy numbers. And 91 is all that the fuel flap (on mine) says; it doesn't mention recommended vs minimum. If we go to the manual, it says my 2009 A4 2.0T can be operated on "Regular" 87 AKI, albeit with reduced engine performance. But how much less? You probably will never know unless you run Premium for a week and dyno it then run Regular for a week and dyno it. Same for what if any loss in mileage you might experience.

The real question comes down to the recent reality where Premium is now 20%-25% more expensive than Regular here in north Atlanta, versus at most 10% more expensive in the past. I highly doubt buying that Premium is giving you 20% more mileage. While the price premium is nuts lately, it still, for me, doesn't add up to a financial obstacle annually. Performance of the 2.0T is already anemic enough, and it avoids my engine having to do a timing adjustment dance going back and forth with knock detection.

Do not confuse the topic of octane rating vs fuel quality. The latter is typically a reflection of vendor, and will not vary much across the octanes from said vendor. That said, there was a BP doc on invigorate additive that did show they put more detergent in the higher octanes, even though the regular octane still had way more than EPA required mins (a reflection of the Top Tier fuel standard). It's hard to say if that will matter unless you want to become the long term test guinea pig.

SeaToSky

My best fuel, an overall basis is Shell V Power Octane 91in combination with the continuous use fuel additive ZVW 239003 along with proper maintenance. On the summer highway I get 600 Km / 375 miles of spirited driving on 50 litres / 12.5 US gallons or 30 miles per US gallon. I am also careful about tire inflation (front rear differential) and I learned to drive from a retired races so it is all about momentum, not stop and go.
I get less results from the other four "Top Tier" fuel providers even if I use the 94 Octane. I am also meticulous about carbon build up with the current DGI setup. In my experience, poor mileage is usually a difference between drivers and their level of understanding of how a n(0.5L)T DGI engine works. Anyway, that is my one Liter's worth.....