Group V esters are interesting, inasmuch as the term "ester" only really refers to a single functional group. The capacity to tailor the "r" alkyl groups around these are infinite, and there are a number of small-batch companies producing highly customised esters for lubricating oils. Biosynthetic Technologies is known for the Estolides - a form of ester that is very resistant to hydrolysis. The other advantage is the capacity to produce sustainable lubricants at scale; this could very well be the future of the industry. Biosynthetic Technologies YouTube Channel: https://youtube.com/channel/UCC-rip-p6HtahQyeQclHBnw Biosynthetic Technologies Website: https://www.biosynthetic.com/005