Welcome to the forum kuapoo!
I use Valvoline 10w-40 in both of my gy6 powered quads. More power can be got fairly cheap by getting larger jets and putting a free flowing air filter on if it doesnt have one already. For high performance parts call RaceWayAtv. Im sure they sell a few things to make your 150 faster.
-------------------------
07 Jetmoto 250 Sport
07 90cc Mini Ute
06 Jetmoto 200 Enduro
06 Jetmoto 200
06 Jetmoto 150
06 Jetmoto 125
04 Yamoto 150
01 KTM 400 EXC
92 WR 250
91 CR 250
88 YZ 80
85 CR 500
83 XL 600
82 XR 200
79 XR 75
79 Odyssey
73 Bultaco 360
71 Rickman Montessa 250
70 Rupp Enduro
69 Honda 50