Originally Posted By: daz
I know little about oil, but from what i've gathered here and elsewhere there are only a very few oils that are true synthetics. Most oils labeled "full synthetic" like castrol are just dino with additives that allow them to call it synthetic. So what then is blend? I know when you're talking about true synthetic, blend means 1/2 dino and and half synthetic. But when the "synthetic" oil such as castrol synthetic is actually dino oil in the first place, what is thier blend? It can't be 1/2 dino and 1/2 synth because it's already all dino with additives. Please explain this to me.
It isn't "dino with additives", they utilize a group III majority base oil instead of a PAO/AN/Ester majority base.
Group III is quite common and is capable of giving performance very close to/indistinguishable from (depending on what traits you are comparing) PAO.
Oils are a blend of bases and additives that allow them to meet their desired performance target. To achieve its excellent low temperature performance for example, Mobil utilizes 30% and 70% PAO in their AFE and EP 0w-20 products (respectively). The rest will be a mix of Group III (Mobil's version is called "VISOM"), AN's and Esters.
A synthetic blend will be partially comprised of a Group III or PAO (Group IV) base and then a conventional (Group II) base, which likely makes up the majority of the blend.