The 40 weight oil is good for abusing the sh!t out of the motor, its heavy duty. But it is heavy. Ford claimed their cars i tiny bit more HP when they started recomending 5w20 over the normal 5w30... Just cause its lighter. Thats sorta why I went with the T5 oil.. Its actaully a 10w30. Heavy duty, yet lighter.

Also keep in mind that roumor has it that all the sut protection in diesel oil isnt good for cats. But Ive never seen any proof of this.

11.45@125,
stock bottom end 6bolt 2g head.
272 hks cams.
Holset hx35
Backyard biult!!