It seems to me that synthetics that are considered group V are about twice the price of Group IV synthetics.
I drive a tuned BMW 135i that runs about 18psi at WOT with full bolt on's. Intercooler, Downpipes with full exhaust, Cobb Stage II tune.
I am considering the following 2 oils for my next change and I am unsure about which one to go with:
Motul 8100 X-CESS 5W40 - This oil is BMW LL01 rated and I am pretty sure that it is a Group IV
Motul 8100 X-lite 0w30 - This oil is not BMW Ll01 rated and I think that it is an Ester based Group V Synthetic.
The 0w30 is twice the price of the 5W40 and I am not sure if it is worth the extra money or not.