HOW DO YOU GUYS AND GIRLS PROVE YOU CHANGED YOUR OIL...I ALOWAYS GO TO DEALERS WORRIED ABUT THEM TELLING ME the oil hasnt been changed...at least dealer does it i have a reciept,and i know for a fact many dealers in my area all different manufactures use recycled oil, and dont do half the opil changes they charge people for...so i know it is best to do it yourself,but how to prove you did it if a warranty issue arises in the future...