my wife has a 2007 hatchback with same EL15 and we run super all the time with no problem.
the error is because of the oxygen sensor, If you reset the ecu the code should go away but if it keeps happening change the oxygen sensor

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All Wheel reflexes. It's what makes a Subaru, a Subaru..... You'll be imprezzed....

Thanks, I'll reset it and see what happens. One of my Co-Workers actually ran into the same problem after changing to Super. A few post I read they stated to change the Cat others said the Oxygen Sensor, Is there something i can do so that i would never have this problem again?

You can decat the car and install a MIL eliminator by Farley (3979650).
Got his name a while back, I talked to him last year so he replaces the cat with a pipe.
I never did because the CEL cleared by itself and from reading on the net it seems to be a common problem with these cars.
Change back to premium and run the car for a week it usually goes away for itself.
Changing the oxygen sensors will not help if the readings are within parameters the CEL will come back.
Changing the cat with a good foreign used one (hard to tell) should prevent it from reoccurring.

Thanks alot I'll change back to premium and see how it goes, If that does'nt work i'll try that guy.

had that same exact problem, what you need to do to prevent re-occurence is remove the two cats and install the two sensor back onto the exaust but the second sensor use a 1/4 inch spacer to take it out of the flow of the exaust gases and you should also replace the sensors if you have the cash. I did this and have been running super in mine for 2 years now with no engine light.

You could buy a anti spark plug fouler that motorist sells and weld it on to move the rear o2 out of the direct stream of the gas . Cheapest fix and if that don't work then you can do what loud expertz said. I question loud expertz did you notice any loss or gain in performance.