Answer : NO NEED, it is not necessary to change oil before GTO treatment since doesn t really make a difference when it comes to improvement whether the oil is new or old for as long as GTO <a href="http://www.sulit.com.ph/index.php/classifieds+directory/q/gto?x=2">http://www.sulit.com.ph/index.php/classifieds+directory/q/gto?x=2</a> is mixed with it, the engine will perform a notch above the norms. 2.