Audi Recommended Gasoline Retailers and Recommended Octane are two very different things and I did a quick explanation on them both since the thread was talking about recommended gas but all the posts ended up being about octane and not why you use the below companies gas.
I know this is a old thread but just in case anyone comes across it like i did they will leave with all the correct information. Audi's Top Tier Gasoline is recommended for the adatives and other detergents that clean out the gunk and deposits that build up inside of the engine.
http://www.toptiergas.com/
Why TOP TIER
The intention of the TOP TIER Detergent Gasoline standards is to create a winning situation for gasoline retailers, auto manufacturers and drivers. Currently, many gasoline retailers provide fuels with lower-quality additive packages that can build up deposits on fuel injectors and on intake valves. Others can build up deposits in combustion chambers and may lead to intake valve sticking. These lower levels of additives can have negative impacts on engine performance and vehicle responsiveness.
TOP TIER Gasoline Retailers:
USA
76 Stations
Aloha Petroleum
Conoco
CountryMark
Entec Stations
Exxon
Holiday Stationstores, Inc.
Kwik Trip / Kwik Star
MFA Oil Co.
Mileage Stations
Mobil
Phillips 66
Quik Trip
Rebel Oil
Road Ranger
Severson Oil
Shell
Texaco
The Somerset Refinery, Inc.
Tri-Par Oil Co.
U.S. Oil
Octane at any USA gas station is measured the same but not all have the same additives and detergents to keep you fuel system and engine clean and gunk free but you can also buy the additive at those gas stations or a Audi dealer and add it every oil change or every service interval which Audi recommends which will do the same thing as Chevron, Exxon, Texaco and Shell except because of the longer interval you are adding a more concentrate version directly to one fuel tank of gas which is recommend to not fuel back up to you have run 95% of that tank through you cars system
Now octane controls the combustion since we have removed lead from fuels way back when. Fuel is more combustible when the octane is lower and more stable when higher levels are in the fuel. Gasoline can com-bust just from pressure not needing spark. this is why all car makes and models have different recommended fuel along with Min/Max octane levels which are in your owners manual Audi usually says in manual and on the inside of your fuel door that 87 octane is the minimum because of there compression ratio (high compression ratio can cause fuel to com-bust / ignite from pressure then spark ignition happens late causing spark knock which is bad for piston heads and cylinders). But most engines fix that by retarding the timing causing the engine not to run at peak performance but cause no permanent harm just temporary stuff like less power and less fuel efficiency. Now if you car only calls for 87 then your just throwing you money away by putting a higher octane in you vehicle it does nothing for performance or fuel economy on stalk cars unless the car was designed to run on higher octane from the manufacturer.
There are 3 different ways to measure Octane.
In most countries, including Australia and all of those in Europe, the "headline" octane rating shown on the pump is the RON (Research Octane Number) is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane. 600rpm test engine.
(Motor Octane Number) (MON), or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load, as it is determined at 900 rpm engine speed, instead of the 600 rpm for RON.[1] MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON, however there is no direct link between RON and MON. Normally, fuel specifications require both a minimum RON and a minimum MON
Canada, the United States and some other countries, like Brazil, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Pump Octane Number
Difference between RON and AKI
Because of the 8 to 10 point difference noted above, the octane rating shown in Canada and the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel.
So the United States and Canada put the same exact fuels through a higher stress test using (RON+MON)/2 which is a average of the two called the AKI showing a lower octane but is 4 to 5points higher than what is listed on USA service stations which give the below numbers the same equivalent as European RON method.
USA/Canada= Europe/Asia
87 = 91/92
88 = 92/93
89 = 93/94
90 = 94/95
91 = 95/96
93 = 97/98
Now any fuel getting closer to 105 to 110 octane usually has lead in it that will cause damage to the catalytic converter which is in all newer model cars unless it is a track car which usually are not required to have one. For my Audi I looked up the price so i could just point this out $335 for after market OEM replacement to $950 for the Audi OEM before instillation.
Originally Posted by eyrah
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