http://www.silkolene.com/productlist.asp?SECTION_OBJ_ID=25245
Silkolene are bike orientated but also F1. Castor with esters are still being used in Bike oils. The car oils are at least 20% ester. The F1 0W20 oil, which I gather is used off the shelf, is about 2 x price but they probably use similar ester content in all synth oils.