HackDevil

I read something that lead to me searching for this info.

I have the 3.0T and have always used 93 octane for the most part. I did use 91 octane just once on the way back from a business trip and noticed that the car felt a bit sluggish.

I tried searching info on the performance difference between 91 vs 93 but can't really find any useful info for our engine.

Does anyone know if there's a real performance gain between them or is my butt Dyno playing tricks.

snagitseven

Octane vs. performance has been discussed in numerous threads around the forums and elsewhere. Anytime you use a lower octane than recommended by the manufacturer, there will be a some loss in performance. What you felt might have resulted in what you felt, however, the difference between 91 and 93 would be barely noticeable, if at all. I believe if you had used regular, it would be more obvious.

HackDevil

Thanks. I know there's tunes that show a real world gain in horse power between a tune for 91 and a tune for 93.

I'm curious if anyone knows the power difference, if any, are in the factory tune. The manual just says 91 Min. So I wonder if by using 93, that if there are any gains in performance.

jjsC6

I fully agree with Snagitseven. Any difference would be incredibly minimal. It can effect responsiveness as it pulls ignition timing advance. But as he said, just going to 91 is not likely to do much. And don't forget you had some 93 octane still in your tank, so the blend was something over 91.

HackDevil

I agree with you both.

I'm just curious to the science behind it. Is the difference 5,10,15 hp I wonder?

uberwgn

Hack, get the car on a dyno and measure the difference between the two fuels !

snagitseven

It's not necessarily a HP difference but an engine efficiency disparity. Here is an interesting Car & Driver article where they tested cars designed for both regular and premium fuels and measured and tracked performance using both fuels in each car. The last few paragraphs on page 2 summarizes their findings on using a lower octane fuel than recommended by the premium engine car manufacturer.

Regular or Premium? - Feature - Car and Driver

DB22

The car and driver feature is not relevant to the OP's question. 91 and 93 are both premium so the difference in a car designed for premium would be compensated by the electronics running the engine. The article was using premium or regular in cars not designed for either so the results would be for using the incorrect fuel.
BTW CA only has 91 for premium and it's only about 20% more than you guys that can get 93.😄

newmoon

I think there might be a tiny difference but only under certain conditions such as very hot temps, or very high engine loads like when you are using maximum super-/turbo-charger boost. These conditions are more likely to cause knocking which is what the higher octane is needed to prevent.

See if you can hear your engine knocking under load. It is a rattling sound like this:

(but it is not supposed to happen when you rev from idle like that, and a modern ECU will react by retarding timing or reducing boost to stop it).

I do sometimes get knocking on my 2.0T when it's really hot and humid here in Florida, when I floor it from low rpm and the turbo hits full boost. And that's even when using 93 octane!

On the other hand, if it's cool and you run the engine lightly such as cruising on the highway, you can get away with using 89 octane (I've tried it with no detriment to mpg), or maybe even 87 octane (haven't tried).

As for how much power you might gain, probably not much. Edmunds dynoed a VW GTI on 87 and 91:
The Effect Of Octane On Its Power - 2010 Volkswagen GTI Long-Term Road Test

The difference was only 4 hp at the peak and 10 hp (5%) in the mid-range.

So if your engine is running fine without knocking on 91 which is what it's rated for, you probably won't see any improvement on 93.

snagitseven

I guess you missed the word "interesting". The article is not just about using different fuels in cars but also goes into to depth about the science of octane which was part of his question. BTW, your post doesn't answer his last question asking about HP difference either.