I am fairly new here and I really can't decide which is the best oil. Up until a few years ago I used castrol 5w30 synthetic in all of my vehicles. I switched to blend to get a protection at a decent cost, however, once I learned how little synth. was in the blend, I switched. i started using 2 qts castrol synth and 2qts conv. ......OK, So I really don't know alot about base oils and additives and was hoping to get some advise. I have been reading for weeks now and am throughly confused and thought I would get some opinions. If you were a short daily driver who changed oil every 3K / 3 months in a toyota Celica would you use Penzoil Platnum 5w30, German Castrol, or Mobile 1 5w30???? Opinions are all welcome and all appreciated.