1) Antimony is one of the Stabilization compounds (as in HOBS) for their Bio oils and esters.
2) it is an excellent FM/AW compound and highly synergistic with ZDDP.
Thank you Pajero for posting it.
I had this VOA of the Bio-SynXtra™ Booster Pak from RLI made at Blackstone 3 time before getting the correct results in 2013.
Not an engine oil, more an oil additive under this form:
http://renewablelube.com/store/motor-oils?product_id=158
Christian