When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
0w30 Castrol Syntec or "German Castrol" is just a different weight of oil. It's thicker and supposed to provide more protection compared to 5w-30.
On the ls1 board a member dyno tested Mobil 1 5w-30 vs 0W-30 GC and the mobil 1 dynoed 4 more hp. But this was on a H/C vette putting down 507rwhp(mobil 1).
It's "supposed" to provide better protection--that's all. I dont think I'd run it on your mod motor though.