The cheapist unleaded plus around here is 2.19 and most places are 2.29 it realy sucks.

 

YES. You must use it.

Besides, think about it - over 10 gallons that difference in price between regular and premium only becomes a few bucks. Don't cheap out on your car.

 

Perhaps it's labeled differently in your area, but in the northeast, regular is 87, plus is 89, and premium is 93 or 94. You need at least 91, period.

 

YES. Its a turbo.

 

I'd like hear why, exactly, one should use premium. Does it just decrease performance or does it damage the engine? If it just decreases performance then that's not so much problem for me if I know I'll be using that tank for around town driving. However, if it harms the engine then that's another matter.

 

In a nutshell, octane is a compression rating. If you use lower octane gas, the gas will ignite by compression and not by ignition from a spark plug. This is called "detonation" or "knocking" and is very dangerous and can damage the engine. There is a knock sensor that can detect knocking and retard the timing accordingly in the hopes of not harming the engine, but you'll lose a lot of performance, and there are no guarantees. Surely everyone here researched such things before buying a car that uses forced induction and an engine tuned for higher compression.

 

I know what detonation is (I did my research thank you very much ), but I was curious if anyone had hard data on WRX's and detonation by varying octanes. Ever since my Dad was told to put a particular brand of premium in his Beemer (I think it was Shell, but I'm not sure) I take manufacturer recs with a grain of salt.
Like someone already said it only makes a few bucks difference on a tank so I doubt it's worth any risk, but gas prices are getting cray-zee here in the Bay Area so I just think it's at least worth the debate.

 

*taken from "howstuffworks.com:http://science.howstuffworks.com/gasoline3.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.

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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You will cause damage to your engine. Turbo charged engines are very susceptible to knocking if you don't use the right fuel/engine management.

 

No, I have not seen anyone that has done a study on what octane levels you can push to what RPMs in a WRX before knocking occurs. You're more than happy to run 87 octane without repurcussion if you never use boost, but it would probably be a waste of a $25K investment. As for brands of gas, it really doesn't matter who sells it to you, it all comes from the same place.