njajr

While I was told by my dealer to use Premium fuel, I noticed that the "requirement" inside the gas filler door says minimum octane of 87 is required. Any thoughts on how important it is to stick with premium gas (assuming Top Tier in either case)?

SYMAWD

Regular is perfectly fine, but published power figures are achieved on Premium.

mej16489

The basic idea is that the higher octane gas helps to prevent engine knock. The car has knock sensors that will reduce the power output to prevent knocking (which is tough on the motor) If you run 87 the knock sensors will trip and the car will learn to reduce its power output to prevent the knocking.

Its somewhat of a one-way street. Once you get knocks and the ECU learns how to prevent it, you can't simply put in higher octane and get your power back. It will take a significantly longer time for the ECU to learn that it can push the engine harder once its been reduce. Typically on a ratio of about 10 to 1.

Ultimately there really isn't even much of a financial benefit to running the lower octane. The typical price difference is generally 0.20 cents a gallon max. So, let say you drive 20,000 miles a year at 29 mpg . That's 689 gallons of gas a year for a cost difference of 1378 over the course of a year ($26 per week) My guess is that's generally a very affordable cost difference for an Audi owner.

uberwgn

If true, that's a break from the past recommendation of 91 AKI in the USA.

SYMAWD

Starting for MY16, the A3 and TT say 87 on the fuel door. Same thing with MY16 VWs using this engine. Apparently for US cars only but published power figures are achieved using premium.

rdA4WtQ5

I was curious and looked up all our Audi Manuals and they all read the same. Premium 91 recommended regular 87 is Ok with less performance. Only the gas cap labeling has changed. If you do the octane math, mid grade is a ripoff and should be avoided. Alternate between regular and premium without running to empty for a cost effective compromise.

Check your Audi fuel requirements here:

Audi Online Owner's Manual

uberwgn

Interesting. I hadn't seen that mentioned previously. Thanks.

a2oc

The only reason I can think of that audi has changed to 87 on the fuel label is to lower the EPA annual fuel cost printed on the 'monroney label'. All cars sold in US are required to run on a minimum octane level of 87. But when you do that, you will lost quite a lot of performance.

BobMar46

At least where I live 91 is not readily available. So to accomplish the recommended octane I would need to use Premium. Cost spread compared to 87 is currently 29.7% higher for Premium. Virtually every turbo on the market recommends and/or says Premium is required. That allows them to show performance numbers for that. The 87 will not hurt the engine. It really comes down to a decision of whether the extra cost is worth the difference in performance. It is a bigger difference in performance in flat out performance numbers than it is based on the way that most of us actually drive the car day to day.

plat27265

For day to day city driving, a loss of around 10HP to 15 HP due to the use of 87 won't make much of a difference. If you do lots of highway driving and drive aggressively or regularly go to the track or take joy rides around twisty and hilly mountain roads, best to use 91.