Segmentation by type isolates the chemical composition and performance attributes that differentiate circulating oils. Mineral‑based oils, derived from refined crude, dominate with an estimated 45% share due to cost competitiveness and established supply chains, though they offer limited oxidative stability. Synthetic oils—primarily polyalphaolefins (PAO) and esters—capture roughly 35% of the market, favored for superior temperature tolerance, lower volatility, and extended service intervals in high‑precision equipment. Biodegradable oils, including vegetable‑based esters and synthetic‑bio blends, account for about 12%, driven by regulatory pressure in environmentally sensitive sectors such as marine and food‑processing. Specialty formulations, such as fire‑resistant or anti‑wear additives‑enhanced blends, represent the remaining 8%, catering to niche applications where safety or extreme load conditions are paramount. Each type’s market contribution aligns with its functional fit, cost structure, and regulatory landscape, reinforcing the overall taxonomy of circulating oils.