Making Zinc Oxide, additive for oil Options

[timothy_nd28]

Is there any Chemist here, that can do a write up procedure to make a zinc additive for the cheap oils at the auto-parts store? My Castro GTX oil seems to be lacking zinc these days, and I really don't want to spend 20 bucks on the additive.

[Madswede]

Uhm ... it's not really zinc oxide that's a motor oil additive, at least not for the purposes of anti-wear and corrosion inhibition.

ZDDP is actually a family of chemical compounds that has a basic central structure around the zinc atom. This is called a "coordination complex" or compound. The chains of hydrocarbons that can branch off of the main central group of sulfur, phosphorous, and oxygen surrounding the zinc atom are called ligands, and as a family of complexes with different ligands they are collectively called ZDDP, or zinc dialkyldithiophosphates. It's actually the structure of all the stuff that goes around the central part that gives the ZDDP much of its desirable properties, especially its solubility in motor oils.

Zinc oxide may be used in part of the manufacturing/synthesis process, but other than some very general concepts of how ZDDP is made that anyone can find on the 'net, I haven't a clue. It's likely a highly proprietary (i.e. a trade secret) process that Castrol came up with, though I'm sure others have their own versions. There are tricks in this sort of chemistry to get just the right amount of each type of ZDDP or closely related complex that really are the stuff that make whole armies of chemists and chemical engineers a helluva lot of money.

In summary, I think you'd need a PhD in organic chemistry focusing on synthesis to make a reasonable go at it, and I doubt it could be done reliably or cheaply enough to justify making it on one's own - it would almost certainly cost quite a bit more than the $20 for the additive.