Engine oil

oil, is oil, is oil. dosn't matter even if its the $1.29/ quart wallmart brand.
the only oil thats better then oil is the man made stuff. change the oil
and filter at the recomended milage/time even if it dosn't look dirty and
your engine will live a long happy life. but this is all just my opinion.
I don't know about. I used some cheap(store brand) oil once before in a Geo Metro I had and it would not hold oil pressure for nothing.