Many conventional additives are effective when first added but can cause problems later.We questioned and investigated. We found that many additives were ill-suited for engines and contained toxic and environmentally harmful ingredients. Also, the ingredients of imported additives are not subject to Japan's penal regulations. We did not want to make the mistake of selling a useless but dangerous additive, so we developed an effective and environmentally friendly product. We named it "ZOIL". Z = Last (ultimate) plus OIL.