Yes, the "C" is for Cheney — I'm just back from Alaska where I personally drilled the first oil-well into once-protected now-exploited national reserves, and then had three heart-attacks all at once!
I know a bit about motor oils, but only from embarassing amounts of time spent researching online.
Basestocks are the essential oils taken from the ground that through refinement become our motor oils. Like many things, there are various grades and qualities for basestock. Most standard, name-brand petroleum motor oils come from Group III basestocks.
Group IV basestocks, those used by true synthetics, are comprised of polyalphaolefins, the molecules that account for synthetic oil's superior lubricity, heat-dissipating, contaminant-trapping, and longer-lasting abilities.
Group V basestocks, the best overall, are polyolesters and actually are not petroleum based, but come from corn.
Synthetic oils require (for several reasons beyond the scope of both this post and my complete understanding) the use of both polyalphaolefins and polyolesters. Mobil 1 is considered a Group IV oil because it contains primarily polyalphaolefins with some polyolesters. Red Line oil is considered a Group V because it contains primarily polyolesters with some polyalphaolefins.
Castrol Synthetic is actually a Group III petroleum oil that has been hydrocracked, meaning guys in labcoats have literally broken the molecules down into smaller components that mimic the molecular structure of synthetics and marketed them as such. Mobil actually took Castrol to court over this, claiming that Castrol was guilty of false advertising by claiming their Group III oil was a synthetic. The judge disagreed and Castrol won the suit. In Europe, however, where labeling laws appear to be more stringent, Castrol is not allowed to advertise their product as a synthetic oil. Understand that the origin of this problem is that Castrol did a bait and switch. Their synthetic oil began as a Group IV, like Mobil 1's, but once they gained the public's trust with a good product, they downgraded their basestock to a Group III without informing anyone of the change.
The big debate is whether or not BMW High Performance Synthetic Oil (which we know is a Castrol product) is identical to Castrol Synthetic. The two products actually have different API and ACEA ratings (BMW HP Synth has superior numbers), indicating that they're not the same oil and that Castrol's BMW brand is better than its shelf brand. Inexplicably, however, neither BMW N/A nor Castrol will respond to requests for clarification on this matter, which is suspicious. Add to that that Castrol is willing to market a product that's not really synthetic as a synthetic, that they originally bait-and-switched their buyers, and, frankly, I just don't want to give them my money.
Mobil 1 is only slightly more expensive, and I know that I'm getting a true synthetic and better product, which is why I choose it.