So i am about to top off the oil in my girlfriends truck when her step dad spots me with a bottle of Pennzoil Conventional and says "Who uses Pennzoil?" Then he goes on to talk about how it is garbage oil and has gunked up several engines he has torn down in the past. He says the only oil to use is Castrol. Dont get me wrong I have no problem with Castrol. I have torn down several Datsun L series engines and Nissan SR engines and have always used Pennzoil Conventional and they always look clean inside. BTW he also made the comment that Pennzoil it sucks unless it has been changed since the 70s. I know it has been changed but i just want some good hard facts for arguments sake.