Just got an 02 z the woman that had it earlier was using reguler unleaded its got 38 thousand miles and im going to a higher octane
now my question is how would i go about doing this and should i check for anything that could have gone wrong from this

 

well, it will automatically adjust to the higher octane
not sure really how you could check to see if any damage is done
i'd suggest running some seafoam in it though to clean out anything in it

 

i was worried that if there is still some lower octane it would mix and be worthless

 

I'd suggest driving it to the lowest fuel amount you can without running out and then filling it up with 92/93 octane(whatever your state runs) with an octane booster. That should be all you'd need to do to "switch it over".

 

kool thanks for the info

 

I say the next time you drive up to the pump just put the higher octane in it. I can't imagine regular octane would cause a problem. The owners manual says for "optimum" performance use highest octane possible. It doesn't say it's required.

 

Octane booster is snake oil, a waste of money. The car was designed to run 91+ gas, low octane gas would generate knock. Hopefully the knock sensor has been taking out timing to prevent valve/piston damage. If she didn't drive it hard, it's probably fine. I'd fill it with 91+ and not beat on it until you run through that gas and get a full tank of good gas.