heynowbababooey

In the USA. Looking to lease an 18’ S4 in the upcoming month. Wanted to know if I should only use Premium Octane 90+? Or are 87 and 89 absolutely fine? Looking forward to the responses.

uberwgn

If you want to follow the engine manufacturer's recommendation, it will state: 91 AKI or better

When we forget, it's always printed on the gas filler door of each car. Very convenient !!

SCarGuy

All new Audi's in the US call for 91 octane. A3's are the only ones specified for 87

SYMAWD

I use 93, but 91 is what's on the fuel door of all Audis except the A3 (excluding etron, S3 and RS 3) and TT (excluding TTS and TT RS) which say 87.

SCarGuy

forgot about the TT, I never see them lol

FWIW in a pinch, if you're stuck in the middle of nowhere, 87 or 89 will work...I just would not push the car at all, as it can be a costly mistake

markcincinnati

It is a "false economy" to use anything less than Premium. Our dealer has -- for years -- urged us to ALWAYS use top-tier.

Our choices (SW Ohio): Costco, BP & Shell -- from time to time, Mobil.

Rarely, rarely a non-top-tier premium.

https://www.toptiergas.com/

The computer in the S4 will "detune" the engine if it detects knock (from using non-premium gas). The thing is, there is a loss of power -- and mileage declines.

Hence the term: False Economy.

mplsbrian

Adding onto what Mark said, pretty much all modern cars have a knock sensor that will pull timing to protect the engine upon detecting knock. However, the thing about knock sensors is that they are a reactive technology: actual knocking has to happen first, and knocks (even a few of them) are extremely hard on an engine. So in addition to the "false economy" of running low octane gas and the detuning that results by doing so, you also have the risk of damage (or at minimum, greatly accelerated internal wear) happening internally within your engine.

To answer OP's question, I run 91 (and 93 whenever I can get it, but I don't ever go out of my way for it).

If one were to find themselves road tripping across the country, or knowingly traveling through areas where stations at all (let alone with 91+) are few and far between, I would advocate carrying a bottle of octane booster in the trunk just in case you had to put some 87 in. A single-tank bottle of it is very small and just a few bucks, and you never know when the nearest station is going to be out of premium (or just not carry it) so while octane booster is definitely not something I would plan to rely on often, a bottle in the trunk is a nice insurance policy (as is a quart of our special 508-spec oil in case you have to top off).

adg44

It is officially tested at 91 octane, so this is the lowest octane that you should use if you want the stated fuel economy and performance.

NHman

OP, should you decide to lease (or buy) a new S4, as others have stated, use 91 or 93 octane. In a pinch, a lesser rating will be okay. Just expect a decrease in power and economy. For me, I've only used 93 octane from Shell.

Comparing the cost of filling up with regular vs. premium, nets you one medium cup of coffee. Meaning small change considering the offset of loss of overall performance.

Best of luck with your decision.

heynowbababooey