Distillates, Petroleum, Hydrotreated Heavy Naphthenic

Hydrotreated heavy naphthenic petroleum distillates are a refined lubricant base stock fraction used to provide viscosity modification and residual lubricity in penetrating oils, metalworking fluids, and industrial lubricants. The hydrotreating process saturates aromatic rings and removes sulfur compounds, reducing the PAH content compared to unrefined naphthenic stocks. In penetrating oils this fraction contributes to the residual lubricant film that reduces re-seizure risk after the initial penetration event. It has lower volatility than the light aliphatic fractions, so it tends to remain on the fastener longer. Ecotoxicity data is favorable compared to aromatic fractions — aquatic LC50 >5000 mg/L fish indicates low direct aquatic toxicity — but like all petroleum fractions it is not readily biodegradable. The H304 (aspiration hazard) classification is standard for petroleum fractions and reflects the risk of aspiration pneumonitis if swallowed, not a vapor inhalation hazard during normal use.