I just aquired a 1993 Toyota 4x4 with the 3.0 V6. The previous owner used Pennzoil in the truck. Growing up I had always heard that Pennzoil was crap. My dad and all his buddies used Castrol oils. Since I've owned vehicles I've always used Castrol motor oils and never had a complaint. Question is: is it okay to switch motor oil brands? I've heard some say that it's not good to change and some say it doesn't matter. What is your opinion of Pennzoil motor oils? I think that I feel more comfortable running Castrol GTX with Toyota oil filters. I just wanted to get an couple of opinions here. I searched and didn't come up with anything. Thanks!