Ok in Australia we have 3 standard unleaded fuel choices 91, 95 and 98 octane. The octane recommended for the RA by mitsu is 98+ here.
I have ran both 98 and 95 and for the difference in cost I can't see the justification in paying for 98 as the performance difference is negligible in a stock RA. Also I can see in USA that you only have 89, 91 and 93 I think.

The question is that if I run on 95 octane is it in anyway going to harm the engine or void my warranty?

 

IIRC, the equations used to determine octane ratings in the United States are different than those used in the rest of the world. Your 98 octane is, more or less, equivalent to US 93 octane. Your 95 should be equivalent to US 91, which is better than CA, NV and AZ 91 (which is what I'm stuck with). You aren't going to hurt anything running your 95 octane, but you will see less performance/power (especially with a tune).

It's really up to you to decide whether the difference in price is worth the performance.

 

Thanks for consise answer to my question it clears up my confusion with the different octane ratings I see talked about here.