Castrol SLX still synthetic??

I just bought a case of Castrol SLX Professional OE 5w30 for my 2001 ALH. A spare SLX jug from my last oil change has "full synthetic" on the label. The new jugs nowhere state "synthetic". Bought from the same supplier (local oil distributor), about 8 months apart. No other changes in ratings, etc on the label. Both state 502 00/505 00/505 01.

Is this stuff still synthetic? Is this some sort of marketing sneakiness? If it is synthetic why change the label?

Could there be two versions of this stuff, one syn and one not? That makes no sense.

-Eric

Castrol ran into some legal issues with the 'full synthetic' printed on the bottle.

IIRC Castrol is using a highly refined group III base stock, while Mobil is using a group IV. I believe Mobil sued Castrol, and Castol had to change some wording. - that was late 90's though...

505.01 oils are semi-synthetic, but I really don't know what that means. US and Euro definitions of what makes a synthetic oil differ. Semi-syn in this case may only mean group III stocks. Perhaps someone with more knowledge would provide me with a link...

Go to over to Bob the oil guys site, they have been debating this for years. Both companies have varying qualities of oil. For example, Castrol's 0-30 and Mobil's 0-40 are highly respected. Regular Syntec is not.