vartanyan

85 is standard issue here in Colorado...

Paul Collurafici

I put in the cheapest I can find. That's always 89 octane. A few times I felt generous and put in 93 octane. I noticed NO DIFFERENCE in performance but did get an extra 20 miles out of those tanks. Not really worth a buck a mile to me... 93 octane is a dollar more per gallon and I take 20 gallons on a fill up.

AlbertQ7

The higher the altitude, the lower octane you need is true for a normally aspirated engine so the air/O2 density is lower... but is that negated since we have a supercharger? Doesn't that compress the air, increasing the density, and therefore increase the octane requirement again? I guess it depends on how efficient the supercharger is, which I have no clue about. Anyone?

mikem33

As I understand it, supercharger volume drops with altitude, just like normally aspirated engines. Since the pump spins at some fixed multiple of engine RPM, the output pressure depends on input pressure in a linear fashion. Turbos, on the other hand, simply spin faster and can deliver the same volume at altitude.
This gets complicated a bit by the fact that the supercharger in our engine has a bypass valve, so it is very likely that the supercharger provides more boost than what the car can use under most circumstances, and the excess gets bypassed under ECU control. I don't notice a difference in acceleration at sea level vs. 6000 feet..... I do notice it in my normally aspirated truck. The relative density at 6K feet vs. sea level is about 0.8.

As for octane: Audi recommends 93 RON, but allows 89 RON, per the sticker on the fuel door. But keep in mind these are RON numbers. The US uses R+M/2 for octane (look at the sticker on the pump, under the number), which at these numbers is about RON - 2. So 87 is the minimum required, 91 is recommended (in R+M/2). There are charts you can google that show the translation from RON to R+M/2 for US fuels; subtracting 2 works for this range.
The manual indicates there may be a slight loss of performance when using 87. I haven't noticed any 'seat of the pants' difference between the two.

Force-1

Damn! I refueled all 3 vehicles at Costco this morning. Premium $2.89; regular $2.69!

Brimstone

I've done 93 on all but 3 fill ups (91) my best gas mileage was actually on a 91 tank (25 mpg, almost all highway though).

Oddly fuelly doesn't put the octane rating in the downloaded spreadsheet, so I can't easily show the difference although its so lopsided I wouldn't put a lot of credence in it.

M0J0

https://www.consumerreports.org/fuel...d-premium-gas/

https://jalopnik.com/why-putting-reg...m-w-1796463139

https://nypost.com/2016/09/20/premiu...oesnt-need-it/

The only way you need to put in premium is if you are going to the race track in a high performance car. So even if you own an Audi R8 you can daily drive on non premium.

Regular vs Premium can be 20-50 cents a gallon more depending on the station. I have seen as high as 80-90cents higher. That is a significant amount of money.

jetsfan101

i remember running 87 fuel in my old vr6 passat and the engine used to knock. Those were the days when audi also recommended 91 fuel. Is anybody noticing completely normal engine/sound performance with 87 fuel? It's about 50 cents per gallon difference here in texas for 87 and 93. So about $10/fillup

If it's money out the window, it would be good to know

M0J0

Modern engines are a different ball game. There is over engineering in engines to meet emissions standards. They can adjust just about everything. It is money out the window.

whyman

did you notice any knocking though? the 3.0T engine is a pretty high compression engine compared to the 2.0T