Premium or regular?

run regular its not gonna hurt anything. premium will, your wallet.

Premium. Not sure what motor you have but most non turbo eclipse s have a 9:1 or 10:1 compression ratio. Must have high octane or the fuel will predetinating before plug fires and before the pistons make it all the way to the top of their stroke.

Will cause loss of performance

whichever the manual calls for...quite certain that it is 91 octane~

Mitsubishi Eclipses with the 2.4 L four-cylinder engine accept regular fuel with a minimum octane level of 87. When equipped with the 3.0 L V6 engine, the Eclipse requires premium fuel rated at 91 octane or higher. The transmission paired with the engine has no bearing on the recommended fuel type.

thank you Racer_X...it takes a real GURU to feel comfortable with sweating out the details such as you've done~ kudos, my brother~

get tired of this whole "will not be happy with anything except 91 or 93 octane...that damned MINI is like a fussy man in a wheelchair~

If you run 87 in the 2.4 you will not be satisfied with the performance. Have owned two of them and it calls for premium fuel.

...darn. yes...only a 1.6 liter but plenty of performance there...wouldn't be there if not for the high-test gas...good point-sir~

Oh 1.6 in your mini. Eclipse is either a 2.4L or 3.0L.