And fuel economy. Doesnt that kinda defeat the purpose.

 

it only defeats the purpose if the correlation is exact - which it isn't. the extra you spend on the gas (roughly $2.70 extra) should get you another 25 miles per tank but which would have to increase your economy by about 2 mpg - i'm not sure - but i didn't notice any increase - or decrease at no matter what grade i use - i think it must just effect the performance

 

I've been using 87 oct. fuel for over 50,000 miles now. No problems with stock setup. Slightly better fuel mileage with less oct. to boot!

 

It's amazing how hyped up this topic gets. It's really pretty simple and the article that was referenced early in this thread nails it.

Octane is simply a measure of how much a gas resists pre-detonation (knocking). The higher the octane, the higher the resistance to PD. Higher compression engines are more susceptible to this. In the old days (before we had the equivalent of a couple of PCs under the hood), you needed to go with higher octane gas in for these engines to avoide knocking. Now, engine sensors detect knocking immediately and adjust timing & fuel mixtures to prevent it. The consequence of this "tweaking" by the engine control unit will be a loss of power and efficiency. How much? Probably not enough to make your car fail to accelerate when you need it and probably not enough to offset the savings of buying lower octane gas.

So, if it makes you FEEL better buying higher octane gas (you want to pamper your baby and want max performance), go for it.

If you want to economize and don't mind trading off some performance to gain maximum value (note the choice of the word "value" here; this is a measure of money + efficiency -- not just MPG), go with a lower octane. You will not hurt your engine. You will not have your car fail you when the train is coming at you quickly at a crossing. You WILL have to endure the riducule of some people on the forum. Just smile at the ridicule and sip the beer you bought with your savings.

That said, I tend to alternate between 93 (mostly and when I find a cheap station) and 89 (switching to mid-grade more often given recent pricing).

Final note: Do NOT feel that you are doing ANYTHING for your car by "avoiding cheaper independent gas" and buying "brand name." ALL of the gas gets to your geography through a set of pipelines that are common to ALL companies. It is ALL THE SAME until it gets to the pipeline depots in your area (this stuff typically gets piped to your area from the refineries positioned along the gulf coast) where the company (e.g., Shell, Mobile/Exxon, etc.) puts in their unique blend of additives (mostly detergents) and trucks it to the stations. ALL gas has detergents in it. If you have some specific reason for loving Exxon's particular brand of Dawn and want to pay $.10/gallon more for it, then by all means, go for it. Otherwise, buy as cheap as you can get and save up for that next mod.

 

I use 93 octane and still hear knocking on my 2012 A6 Audi...what might be the cause??

 

I just ran a 1,000 mile trip in my 2000 A6 2.7t. Down on 87 and up on 93. Mostly on the interstates doing about 60 to 80 mph. On 87 I got 24 mpg on 93 I got 23.2 mpg. Not a significant difference. I also noticed no performance difference. Just saying.

 

At the Sunoco station on Fridays I can get Premium for the same price as Mid Grage... 93 octane for about $3.30 right now. Got to love TN gas prices... and it's winding mountain roads!

 

Something is not right! Better have the dealer check it out. Sounds like a timing issue.

 

You guys in Tenn. Are lucky buy your food at kroeger and get .10 off a gallon or more! In new jersey premium is $3.56 -$3.70.we get no discount what so ever! In new jersey it is against the law for us to pump our own gas! I cant wait to move back home!

 

That's for sure... I grew up in Jersey but got out when I was in my early 20's. My sister lives in PA but drives over to NJ to get gas because she does not like to pump it and it is actually less expensive in NJ. In the little town of Morristown, TN we have a great little restaurant called the Jersey Girl and they have a big sign saying Jersey Girls Dont Pump Gas... most people have no idea what that is all about. TN is still a well kept secrete!