Most modern engines have KNOCK sensor and will retard timming if they pre-detonate. Just not sure about Forte...... I use regular because there's no use for "slower" fuel and it cost too much for little gain!I have an ex too, and have been asking myself if its worth putting high octane fuel!
It seems that if your engine is pinging or it pre-ignites, then you need to use higher octane fuel. i just read this here, in CanadianDriver, a reliable source of info.
the only question is: is the ex engine susceptible to pre-ignite? does anyone know? How do you find out if your engine pre-ignites?