I have a 2006 Ralliart, and the engine light came on a couple of weeks ago while on a road trip, and I've been getting extremely poor gas mileage. Approx 250km to a tank, running premium octane fuel. And when it idles, it sounds as if it wants to stall at times. and the exhaust smells really bad.

Any idea what is wrong? The nearest Mitsubishi dealership is about 500km away.

Since your running on premium fuel that may be causing the problem. I have an 05 lancer ralliart and mitsubishi recomends using 87 octane fuel. The higher to octane the hotter it will burn, but octane also means how much compression is needed before ignition. That may be the reason why engine light is on. My friend has a protoge and when she ran it on high octane fuel engine light was always on but since she went back to 87 it turned off. Also with gas hitting 109.0 per liter now 87 sounds better

You can take it to any mechanic who can scan the ECU and get a code for the engine light. Sounds like a O2 sensor issue, but don't do anything until you get the code.

I was thinking something is up with the catalytic converter. But I'm no mechanic by any stretch. My stepdad also suggested disconnecting the battery for a few hours, he said it would reset the computer but he isn't a mechanic either so I don't know if this is a good idea.

And I'll try using a lower grade fuel. I'll have the code checked if I ever get a day off work.

Did you manage to resolve the issue with your Engine Light? Was it the O2 sensor?
Mine has been coming up when I step on the gas. Haven't check it out yet and was wondering if it really is the O2 sensor or the octane level in the fuel.

my oxygen sensor is toast, a new one is on the way. I also had the injector seals replaced, which has improved my mileage. Whether the two issues are related, I have no idea...