I recently changed the supercharger oil in my Eaton M90 equipped
Pontiac Grand Prix GTP. I took pictures and created a guide to help
other GTP or GS owners. You should be checking the s/c oil every 30k
miles and topping off or I recommend changing it every 50k miles. It
only costs about $15.00 for two 4 oz bottles of s/c oil from GM.