ShaunComan

I can not vouch for the IS250 recommending premium and really needing it but it does play a factor. Myself and my crew run GST Eclipse and WRX Impreza and unleaded is abuse. It causes horrible idle and just ugly on the turbochargers performance. Higher octance withstands higher compression before detonation, so i would not be cheap cause if the motor is designed to run at higher compression and you use low octane don't be surprised if it causes engine knock later on. It's designed to run higher octane not to be expensive but to not have preignition or cause air/fuel struggle.