What wieght oil do you use?

20w/50 Castrol gtx in everthang except my ole Cummin's, and it git's the Rotella T-40 treatment....

I had a discussion with a factory rep once about oil and the factory recomendations(oil listed in the handbook)...He told me that the book wuz written for a northern climate, and didn't take into consideration that sum ov us lived in the swamps, and deserts...So, the 10w/30 can stay up north, kuz we do tha 20w50 thang here in the swamp...He also recomended synthetik, but me bein old and hard headed, it juss stays cleen way to long for me...My way ov thank'in is when ya oil git's dirty, it's cleen'in yo mota...when it stays cleen....well, U know.......If ya ever tore down a motor that used quaker state, U'll know exzakkly what I meen!!!!...REX