Gas quality

[hanskra]

Hi,
I have been wondering what happens I fed the RS6 only mid quality gas (89). Top quality here (Canada) is occasionally so ridiculously expensive, that I could trade up some horses for coins.
Has anyone used 89 octane (or even 87?) gas before? What happens? Would it damage the car or just tame it down a bit? Any answers are very appreciated. Happy RS6ing.

[DuckWingDuck]

Your car, like all modern cars will adjust its performance down to the level of the gas that you use. However, I don't think anyone would recommend pro-long use of this. And, Fifth Gear did a review on the various octane of gas relative to performance a few years ago and they found that higher octane did nothing for regular cars but did make a difference for high performance cars like ours.

[JavierNuvolari]

I was wondering the same thing the other day. Recentrly Shell V-Power arrived to the market and at all Shell stations it replaced the common 97 octane. Do any of you guys know what's the difference between V- Power and regular fuel ?

Saludos!

[BigRick]

hanskra,

Keep in mind that North Amarican (including Canada) measurements are a bit different than Euro measurements.

Our 89 is almost equivalent to 94 in Europe according to what wiki's saying.
http://en.wikipedia.org/wiki/Octane_rating

My testings (under uncontrolled environment) have shown that running 89 or 91 in Canada is worth the extra money, has you do get more mileage (about 10-15% in my case) and that compensate for the extra money.

If you want to do the test, don't just measure your mileage over a single tank. It took about 3 full tanks before the difference start showing on my RS4.

I hope it helps,

[hanskra]

Thanks for your responses. I kinda read into this, that driving base octane is technically acceptable without damage, but maybe not smart because of mileage concessions. I will follow my averages and try to put a number on the 'loss' of power too. As long as it's just a trade of, and not causing engine damage, this is ok. Again, thanks, and happy RS6ing.

[Hy Octane]

I wouldnt do it.. Can cause lotsa problems internally.. Knocking and pinging to mention a few.. The cars ECU can retard the timing only so much and then besides lack of power, problems can arise.. Remember, the damage you might do to this motor will cost thousands more to repair than the extra you would pay over a lifetime for the proper octane (91ron min).

[DuckWingDuck]

paul! How you doing man? We should do another get together when I come home in a few weeks.

[BigRick]

I wouldnt do it.. Can cause lotsa problems internally.. Knocking and pinging to mention a few.. The cars ECU can retard the timing only so much and then besides lack of power, problems can arise.. Remember, the damage you might do to this motor will cost thousands more to repair than the extra you would pay over a lifetime for the proper octane (91ron min).

Refer to my post earlier and you'll see that it's virutally impossible for us in Canada to go any lower than 91 RON as we have 87 MON minimum (in normal gas stations)

RON and MON have a difference of about 4-5 points due to the averaging done on the MON scale.

RON is mostly used in Europeen Countries and MON mostly North America.

So running the lowest grade available in Canada is still "OK" even if not recommended it shouldn't cause "trouble" as it would if you were using 87 RON.

[hahnmgh63]

In the U.S. we actually use Pump Octane which is R+M/2. If you use too low of an octane fuel in the RS6 it will first retard timing to a certain point to stop detonation then it will reduce Boost. How far on each, possibly only a chip tuner or an engineer at the Audi factory knows for sure. In the U.S. all Audi's show 91 PON (R+M/2) which in Europe is listed on the cars as 98 RON. Who knows if you will damage your car, Audi lists 91 Pump Octane min. probably not but you are relying on the Motronic to run in a non-standard kind of backup mode. In the U.S. by region our premium can go from 90~94 Octane. In the Northwest we have 92, and with my car chipped, if I am planning on a track session or spirited club driving I will raise that to 93~94 with Booster or addition of 100 Octane Unleaded race gas. It doesn't help to raise the octane past the cars requirement as Higher octane generally has lower BTU's. But what is our cars requirement? Who knows. Under full load on a hot day, it is higher than easy driving without full boost on a cool day, probably by as much as 10 octane points. MGH

[Bigglezworth]

My Volvo and Buick both run more boost than the Audi and there is no question they both perform better on higher octane fuel. I frequently run 91 premium for regular in town travel and then blend 87 low grade with high octaine race fuel for the track. Add to that the continual increase in gas prices and I then opt to run 87 low grade for all road trips where I'm cruising along at low RPM on the highway. Regardless of the engine power and the turbo charging aspect, running high power engines like this would see no benefit from the lower grade fuel at low RPM's.

Tim

[skiwi]

octane is correct, all bets are off if you go too low - iirc it is 95ron. fine for one or 2 fills, but no longer.

an engineer explained it to me in terms of percentages (a long time ago mind, so memory serves...) i.e. you have to cater for the driver of a car such as the rs6 planting boot @10,000' with low octane fuel and expecting the engine not to grenade...

[Aronis]

just my two cents

I drive to Massachusetts to visit and on the way there I get 23 mpg on 97 octane. After filling in Massachusetts with 10% ETOH gasoline I get 19 mpg.

So the alcohol content drops MPG significantly.

And that's with about 1/3 tank of "good gas" and 2/3 tank Massholia gas. I suspect those who live in Mass get worse miliage.