I found this over on another forum when I was doing a Google search for the history of GC.... Pretty interesting....
Castrol 0W-30 is a very unique oil in that it's very fluid at colder temps, but has a tenacious oil film capability at extremely high temps. It's inherent viscosity spread would seem lots wider than the 0W-30 numbers suggest. At the center of it's unique capability is a component called an oligomer. An oligomer is a compound made from single strands (monomers) of molecular material, linked together in varying numbers less than 5, to make different fluids. Fractions of crude oil such as parrafin wax (slack wax) and polybutane (plasticizers) are examples of oligomers. The oligomer in Castrol 0W-30 is a very cutting edge synthetic fluid sourced from Ketjenlube, a big name additive supplier to the lubricant industry. The actual compound was developed by Kyocera in Japan and the formula was sold to Ketjenlube. So your German blended oil has some Asian heritage . The specific oligomer is a small cut in the overall oil make-up, right around 5% or so. It is very thick on it's own with a kinematic cSt @100c viscosity of >200. Thats pretty [censored] thick. Racing gear oils have 100c cSt of 140, so imagine trying to pour some of this stuff at room temps. You might be there awhile. Anyway, what this compound does is attach itself quite easily to all the other esters in the lube. It keeps the film together when the ester film alone would start to fail. Its what creates the "cushioning" effect and dampens noise in high shear and rotational zones such as the valve train. Thats why so many folks comment on how much quieter and smoother their engine seems to run. When 0W-30 was first introduced, it had a pronounced green tint and a sweet smell. This was due to the specific oligomer and ester content. Over time the oligomeric component became expensive, so Castrol reduced its content a bit. It bumped the more common ester content to make up for the loss and produced a fluid more golden in color without the sweet smell of the green stuff. For all intents and purposes, it was a match to the older green formula in routine applications and no UOAs (used oil analysis) have shown any discernable difference between the two. Castrol is a blender of lubricating components, (it manufactures very few on it's own) and as such, can make "miracle" fluids such as this. Exxon/Mobil is a lubricant manufacturer and usually blends components of it's own making. When it needs "help" in producing a specific fluid that it can't with it's own components, they turn to additive suppliers such as Hatco to provide what they need. Still not as broad-spectrumed as Castrol, but they are pretty [censored] close in most respects. Sorry for the long-winded chemistry lesson, but I just wanted to shed some light on what makes the 0W-30 special.
