Extract from UK forum - RS246 thread.
Below is an article written by John Rowland, Silkolene/Fuchs Chief R & D Chemist for 40 years.
Costs of synthetics vary considerably. The most expensive are the �Ester� types originally only used in jet engines. These cost 6 to 10 times more than high quality mineral oils. The cheapest synthetics are not really synthetic at all, from a chemists point of view. These are in fact specially refined light viscosity mineral oils known as �hydrocracked�. These have some advantages over equivalent mineral oils, particularly in lower viscosity motor oils such as 5w-30 or other oils with a low �W� rating such as 5w-50 etc and they cost about 1.5 times more than good quality mineral fractions.
We use several different grades of this base oil, where appropriate. This is the �synthetic� which is always used in cheap oils that are labelled �synthetic�.
Yes it�s a cruel world, you get what you pay for!
Now, you may ask, why are these special mineral oils called �synthetic�?
Well, it was all sorted in a legal battle that took place in the USA about ten years ago. Sound reasons (including evidence from a Nobel Prize winning chemist) were disregarded and the final ruling was that certain mineral bases that had undergone extra chemical treatments could be called �synthetic�.
Needless to say, the marketing executives wet their knickers with pure delight!
They realised that this meant, and still does, that the critical buzz-word �synthetic� could be printed on a can of cheap oil provided that the contents included a few percent of �hydrocracked� mineral oil, at a cost of quite literally a few pence.
So, the chemistry of �synthetics� is complex and so is the politics!
The economics are very simple. If you like the look of a smart well-marketed can with �synthetic� printed on it, fair enough, it will not cost you a lot; and now you know why this is the case.
But, if you drive a high performance car, and you intend to keep it for several years, and maybe do the odd �track day�, then you need a genuine Ester/PAO (Poly Alpha Olefin) synthetic oil.
This oil costs more money to buy, because it costs us a lot of money to make, very simply, you always get what you pay for!
Mobil 1 = PAO
Motul = Not all are proper but believe V300 is Ester
Silkolene = All Pro S and R are Ester
Castrol RS = 10w-60 Hydrocracked (SLX 0w-30 PAO)
Millers = Hydrocracked as far as I'm aware
Comma - part of Exxon Mobil = AVOID definately hydrocracked
Shell = Most are hydrocracked, there are some PAO's
Carplan Triple R = Hydrocracked
Fuchs Supersyn SL range = PAO
Total = Some PAO, most hydrocracked
Valvoline = Hydrocracked
Redline = Most Ester
Royal Purple = Most Ester
It seems that some of the oils are UK specific, but I've seen a few of these here - I've always discounted the Fuch range , but seems like the Supersyn might be the go.
I'm not saying the Castrol is not good, I've used that and the Shell Synthetic in all my cars but it is interesting that they are not really what they claim to be.
Iain - Brisbane
S4 B5 - GIAC Stage 2+ (his)
A4 B6 TQ - APR Stage1 (hers)