Which octane fuel should i use

Seeing as the 05 spectra isn't a high performance vehicle, 87 octane is fine. You can run 91 or 93 but studies have shown that there is no real benefit in running a higher octane than recommended unless you have issues with engine knocking.

Thank you

Can I use e 85 gas in my 2003 kia spectra?

What the first guy said is wrong on some parts you can run any of them but higher octane means better burn and combustion u also get better gas mileage and silo get increase to performance and engine life time