hummerston

Personally i find that my car has better detonation and a bit more acceleration , i find it considerably better , and on a pervious post i noticed someone say something about if your on a highway it makes a difference in mileage , but in the city it won't improve your mileage at all , and thats fully true. So again yes again , there is a difference

A4Avanti

This is pretty much how i think and what ive experienced,
does your car say Minimum of 91 octane, then for s**ts sake dont cheap out and put 91 octane in it. As for the 94 octane, once on a road trip it made a difference instead of 900km/70l tank on 91 oct and 974km recorded km on 94 octane, so i did notice a difference.

my $0.02

USPAVANTWANTED

Higher Octane is better for your car if it is recommended for that engine. I ran 94 octane in my stock Corolla before driving a B7 A4 because I wanted to brag to my friends that I could afford it, did not help one bit for fuel economy nor performance. In hindsight, I realize I was just throwing money away, silly really. Live and learn. Octane rating has nothing to do with how "clean" a fuel is, although it may be cleaner depending on where you buy it.

cheeba and mikeh are bang on with their comments, but mikeh there is no more Petro Refinery in southern Ontario. Regions have plenty to do with where the fuel you fill up with is coming from. Since the shutdown of the Petro refinery in Mississauga not long ago, most, if not all, gas stations in southern Ontario get their fuel from Imperial Oil (Esso), Suncor or Shell operations in Sudbury or Nanticoke. Suncor has a refinery operation in Sarnia but most if not all of their retail operations, Sunoco, have been sold to both Husky and Petro. They now supply those who will buy their fuel. (Agreed, the tanker that delivers fuel to your local station will not necessarily give away the supplier of your fuel, they could simply be contracted to deliver it even the bigger players). From industry insiders, I have heard that the bigger players do not necessarily supply their retail locations exclusively. Petro-Canada stations use whoever will sell them the fuel at the lowest price and get it to them under contract, since their refinery closure. They add their own additive mix after. The smaller players likely do the same.

Judging by the poll results I guess Shell has developed a very good formula of additives. I have been filling up with Esso because of Aeroplan point collection, but will try Shell to see if I notice a difference in performance and/or fuel economy (have an Air Miles Card as well). Thanks to this forum for the poll!

Will update.

mikeh

Higher Octane does not equal better gas mileage. In fact it could be the oposite since companies normally use ethanol to boost the octane level and ethanol has less energy per gal than gasoline.

Octane is simple the anti-knock characteristics of the fuel.

My $0.02 ....... unless you are tuned for 94 put in 91. Stay away from ethanol based fuel if possible.

A4Avanti

Hey mikeh, you are most likely right that higher octane doesnt = better milage but ive done it twice where i filled up with 94 oct when it was available on 1500km road trips and both times i got better milage. i didnt drive any slower or faster or have more/less weight in car. just generally noticed better accelaration and 50-75km more per tank.

but maybe i was imagining, i guess the point is, if car says min of 91 octane then fill er up with 91 octane.

a4rob

yes however running higher octane fuel in a car designed to run on higher octane fuel will equal better gas mileage. Same goes for cars designed to run on 87, 91 or 94 wont benefit but on our audis it will.

mikeh

You may very well have experienced better mileage thats not for me to judge. My assumptions are based on theoretical and mathematical conclusions.

Bottom line here, and I think it was you that said it...... If your car is tuned for 91 then use 91 otherwise you are most likely wasting your money.

sabgog

differences between 91 and 94 have nothing to do with filtering. Its the ratio of iso-octane to heptane. the higher the ratio, the harder it is to ignite. so when you have a chipped engine, or turbod vehicle, you need a fuel that is harder to ignite to prevent pre-ignition and hence, detonation. using 94 on a vehicle designed for 89 or 91 shouldnt help you, and in fact could hinder it, because it will be harder to ignite than the ECU will be calculating for.

USPAVANTWANTED

So I've tried both Esso and Shell for a few fill-ups each and I do not see a difference in mileage nor performance.

Interesting event transpired recently. I was minding my own business driving along for about 30 minutes at 100km/hr and then came to a stop light. It turned green and I accelerate only to find a big light-grey/blue cloud of smoke coming out of my tail-end. I thought my car was on fire! It keeps on smoking every time I give it gas, but no interruption in power, no engine light, no oil low indicator. Essentially everything normal except the smoke coming out. I pull over, switch it into Neutral and rev the engine in the hope that it's a bad batch of gas and let it go through the system. After three or so minutes of this all is well.

Has anyone experienced this before? Any recommendations?

Cheers

janz3n

wow, where did the people saying octane raitings have to do with the cleanliness of the gas get their info from? crazy.