I'm the same with motor oil .I use full synthetic on the three vehicles and Toro mower and regular in the old tractors .The vehicles because of low usage and the mower with only 25-30 hours per year gets changed once a year .The tractors about every two years. I just wait until named brands go on sale and stock up .Doesn't make me much diff if it's Valvoline or Quaker State or Shell .I've heard of all this so called premium stuff like Royal Purple etc but I don't give that much of a thought or credit but again that's none of my business .