Originally Posted by Zimp13
i think that castrol R is fully synthetic. Review :
CASTROL FORMULA R SYNTHETIC 5W-30
A synthetic 5W-30 viscosity engine oil which enables faster acceleration with excellent engine protection and performance. If offers excellent engine cold start responsiveness and contributes to increased fuel efficiency. Recommended for highly tuned, four cylinder engines and latest technology engines requiring 5W-30 or 10W-30 viscosity. Approved for use by Porsche, VW, Audi and Mercedes-Benz. SAE 5W-30, API SL/CF, ACEA A3/B3/B4