So you think that all these "Synthetic" oils available for sale in the various stores around the US are true PAO based Motor Oils. Think again. PAO or Polyalphaolefin is the main lab produced synthetic base for Group IV stock Synthetic Oils. Base I, II & III are all dino oils. I'm being really concise on this as it can be researched elsewhere, I'm just posting it to get the point out to the masses.
Since a 1997 court case brought on by Mobil against Castrol (in the US), and subsequently won by Castrol granted anyone to produce their non-PAO Group III base oil and sell it as a full synthetic, again, ONLY in the United States because anything can be bought or decided by the wrong people (courts, not scientists) in the US. So, since 1997 there has really only been one true synthetic oil available for sale in the United States, Mobil 1.
Well, I'm letting everyone in on a little secret. Castrol DOES sell a true synthetic in the US, it just doesn't make it here (which is fine by me). Autozone sells Castrol 0w30 "European Formula" Syntec. Look for the "Made in Germany" on the back of the bottle. See, in Europe the BS that is allowed to fly in the US isn't worth squat before a real set of government standards groups as in Europe. This is one of those few. Castrol SLX (now Castrol Edge). Note again, there are no other versions of Castrol or any other brand you can buy in a store on any given day other than Mobil 1 which are true synthetics.
There are racing specialties and what not, and "Amsoil" which while a true synthetic has some of the sleaziest marketing people in the world. Contrary to what they'd have you believe, Amsoil isn't the secret oil that most race teams use. In my 10 years of Rallying, Hillclimb and Time Trials I believe I've seen Amsoil once. Most people either use a high end conventional from Castrol or Valvoline, or Mobil 1 Synthetic.
Either way, if you DO look at the various tests online, you'll find that Castrol actually does indeed beat Mobil 1 on many levels (though not all), so either really will do well for your synthetic needs. Mobil 1 is generally a little on the thinner side of its viscosity rating (high number), whereas German Castrol (as it is referenced (or simply GC)) is a little on the thick for its equivalent viscosity rating.
If you are running a high performance engine, a turbo engine, a supercharged engine and/or care simply about providing your engine the best care you can in terms of motor oil, you've got those choices for synthetics and nothing else. Caveat emptor.
And if anyone is wondering, the reason why I specifically went for German Castrol is because it has been pretty much designed for the German motor manufacturers. It is the only oil in the United States (synthetic) that passes the stricter of VW, Audi, Mercedes, Opel, BMW and Porsches requirements for engine oil. I drive a Chevrolet Optra5 these days since selling the VW Bora Sport 1.8T and it is powered by a modern evolution of the 1st generation Iron Ecotec by Opel, which just happens to be produced in Melbourne by Holden (GM Australia). The engine is happy now, getting the fluids it truly wants.
Till next time