Pennzoil has invested hundreds of millions of dollars to develop quality hydro-isomerized (hydrowaxed, hydrocracked) refining technologies. And when Consumers Reports tested oils about 10 years ago, Pennzoil was one of the few companies where the oil vis on the label was consistently the oil vis in the bottle, and their products trended to stay in grade (shear resistant) well. So I say they are a first rate "biggie", with all the good and bad. QC in the bigs is only fair across the board in my opinion. That is why I tend to use products that I have analyzed myself in our Lab, and which have showed high quality, innovative additive technology, pure base stocks, etc. This includes Lubrication Engineers 8130 engine oil, and 607 gear oil (90w), Amsoil Series 2000, Pennzoil Multi-Vis (and some of the old Turbo oil before it was discontinued), Red Line, Motul, and a few more.