[s-cars] Synthetic oil weight rec's

[racingiron at comcast.net]

>> I like Syntec myself. Don't forget that Mobil 1 is no longer full 
>> synthetic as of about 4 years ago. 
> 
> I'm confused. 

You're not alone. I'm not a brand loyalist (I currently use both Castrol and Mobil), but it's funny to read someone recommend Castrol and berate Mobil 1 as not "full synthetic." More than ten years ago, Castrol took some conventional stock, heavily modified it (hydroisomerized), and called it synthetic. Mobil sued for false marketing, and the case made it all the way to the SCOTUS, which decided that these Group III oils are sufficiently modified and perform well enough to be considered "synthetic." AFAIK, group III oils can't be labeled "synthetic" outside of North America. 

Mobil held out with a pure PAO (group IV) base for a while, but even they mix in some group III these days. It's rumored that they still have more PAO than most other major "full synthetics." The kicker is that the group III/IV mixture actually has some benefits over strictly PAO due to better compatibility with additives and such. Today's "synthetic" oils are so good that group III/IV content shouldn't really be a deciding factor in your choice. Get the weight right, change it regularly, and save your worries for something else. 

Eric R. 
'86 urq 
'92 urS 
'93 urS