I know that this subject has been beaten to death, but...

What is the best dino oil to use in our 4cyl OHC engines? I'm maintaining two b23's and a couple b230fs. The '85 and '86 have their crankcases filled with Castrol GTX 20w50 at the moment. The '83 has Chevron Delo 10w30 in it, and the '84 is doing time on Pennzoil 10w40. I'm uncertain about what weight I should be using. IIRC, Volvo recommends 10w30 for these cars. However, I live in the SF bay area, where the ambient temp rarely ever drops below 50 degress. I am self-employed and spend several hours on the freeway/highway everyday. I drove almost 65,000 miles last year alone. For these reasons, I've opted to switch to 20-50 on the cars that I drive the most, the '85 and '86 wagons. I figure that they don't need the cold weather protection that the lower weight would provide, and I think that the heavier oil provides better protection at the other end of the spectrum given my driving habits (high sustained rpm's, more heat generated by the engine, etc.). Is this generally a bad idea? My only concern is that I might be gumming something up with the heavier oil. Will it put more stress on the pump/sump? Saw something in the archives about only using 20w50 if the engine had an oil consumption problem (not the case). If it's really too thick, what is this going to do to the engine?