If you want "real" synthetic oils, you must purchase 100% synthetics, such as, Amsoil, Red Line, Total, Motul, Mobil EP and all synthetic oils that are sold outside the USA with the same exact name here AND are imported into the US. Even though Castrol Edge costs big bucks...it is NOT 100% synthetic and most other Mobil 1 oils are NOT 100% synthetic. If Royal Purple won't put into writing that it's 100% synthetic or that it isn't hydrocracked, do not believe it's 100% synthetic! Most all the "fully synthetic" oils found on the shelves in the US are "fully synthetic" legally, but are made from out-of-the-ground oil and are considered "hydocracked" or super refined "dino" oils or Group III oils. Note the date of the API Group designations in this thread...it's from 1999 and is outdated! 100% synthetics usually cost more (Total is the least expensive that I've found). Why the deception? Back in 1999 Mobil took Castrol to court because Castrol Syntec claimed and still does claim to be synthetic oil (it's hydrocracked) and Mobil (and no one else) could sell their 100% synthetics for the same price as Syntec. The case was arbitrated out of court by someone NOT knowledgeable in lubricants and Castrol won and was allowed to sell their "hydrocracked" products as "fully synthetic". Mobil and everyone else said great and with few exceptions (see above and there ARE more 100% synthetics sold in the US, but not many), sell hydrocracked/super refined "dino "lubricants as "fully synthetic", BUT only in the US! Being the court case was arbitrated in the US, nowhere else in the world can a container of oil/fluid say synthetic, UNLESS it's 100% synthetic (made from 100% synthetic base stock, i.e., PAO Group IV or Ester Group V). Red Line is the only Group V that I know of and has the highest flash point that I've seen. That's why I use it everywhere in the vehicle! Check this URL for more info:
http://en.wikipedia.org/wiki/Synthetic_oil 