Originally Posted By: aquariuscsm
About some saying they're "similar" and not being different oils. SN rated RP has been said to be "similar" to Valvoline here on this site via analyses,but they are two completely different oils. A set of biological twins are "similar",but they are two completely different entities.
That is quite true. But, "completely different" is a very subjective phrasing. One could argue that Valvoline Synpower 5w-30 and Valvoline Synpower 10w-30 are completely different oils.
As I stated before, I believe them that Synpower and Napa Synthetic are different oils. But, when two oils come from one blender with a similar additive package and fairly similar base stocks, and carry the same certifications, they tend to be a lot more similar than different. It's not like one is an A3/B4 with a calcium/magnesium package and the other is a highly friction modified ILSAC oil with a calcium package.
In the same vein, Quaker State 5w-30 SN/GF-5 and Formula Shell 5w-30 SN/GF-5 are likely a lot more similar than are Quaker State 5w-30 SN/GF-5 and Rotella 15w-40 CJ-4.
In the end, I'd be content with Valvoline Synpower or VWB or Napa conventional or Napa synthetic. Here, Napa regularly has their stuff on sale, and would save me from the Walmart experience, where it's easiest to by Valvoline.