We should also throw in
where the get their oil. If they were around here I would use Sunoco oil, seems to be the best of the bunch. Of the stations that are available here in order of worst to best IMO and where they get the oil. I wouldn't by from:
Exxon
Cheveron
Texaco
CITGO
Valero
BP
That leaves
Shell
Conoco
I guess I need to bit the bullet and do a GNG conversion or electric. "Sigh"