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With the limited amount of boost in a stock 1.8T, I doubt that the compression ratio is increased enough to actually warrant anything over 87 or 89.

That said, my chipped baby gets 91 or better.
 

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yea i agree that my dealer is pretty stupid, but i think that running a lower octane gas in the winter when the temp is 30 below 0, it might just actually help. yeah i thought that the whole pinging thing was wrong, but burning at a lower temp has got to help in cold weather. hey i can get 103 and 115 octane gas from the pump at this one place, so would those octanes damage the engine?
 

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yea i agree that my dealer is pretty stupid, but i think that running a lower octane gas in the winter when the temp is 30 below 0, it might just actually help. yeah i thought that the whole pinging thing was wrong, but burning at a lower temp has got to help in cold weather. hey i can get 103 and 115 octane gas from the pump at this one place, so would those octanes damage the engine?
 

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i dont know too much about cars.. but i know a little about science and how an engine works.. id say 103 or 115 cant hurt your car... it just burns slower and cleaner than lower octane gas.. as for lower octane gas burning at a lower temperature im not sure that that is true. pinging occurs when the gas explodes instead of burning - i could maybe see it exploding easier in the winter -- which is bad .. this make sense to anyone else?
 

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pinging occurs when the gas explodes instead of burning
Pinging occures when the fuel/air mixture is ignited by heat before the piston is at top-dead-center. The "ping" is the sound of the piston trying to go back down the cylinder when the rest of the rotating assembly is still pushing it up. The only thing octane does is raise the temperature point at which the fuel/air mixture can be ignited by heat that is caused by high compression or hot carbon deposits. This allows the spark to ignite the fuel air mixture instead of pre-ignition by heat. The 1.8T gets it's higher compression from the forced induction of the turbos boost.
 

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ive been running 93 since feb and have been logging my milage vs gallons ( aka mpg)

i recenly switched to 87 due to the rate hike ( 1.898 for 87 and 2.020 for 93) i will continue to monitor my mpg to see if there is a sudden drop
 

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If you're using lower than 91, I'd recommend using a vag com to monitor for knock & for timing retard.

In winter the intake air should be colder, resulting in less chance of premature ignition. But the air/fuel mix will still burn at the same temperature when ignited, so the chance of engine knock is still the same (secondary explosion of fuel-laden exhaust gas as it leaves the cylinder/enters the exh. manifold). I'd stick to the 91 all-year-round.

An extra $2 per fillup is a small price to pay for minimizing distress to your engine.
 

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From: http://auto.howstuffworks.com/question90.htm

"The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting." [Hence, increased likelihood of premature ignition w/ lower octane]

"The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more."
 

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I put 89 in for the first time since I bought the car in December because I just couldn't bring myself to pay over $2.00 for a gallon of gas. I know the $0.08 per gallon was only about $1 at the pump (1/2 tank) but it is psychological, I don't like "Big Oil" aka OPEC. So far the car doesn't feel different, but it was only 1/2 tank.
 

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gas

Just talked to my mechanic. Octane 89 is fine, but regular isn't such a great idea- carbon deposits on the valves. Could get an induction cleaning though- 100bucs.
 
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