Lubricating oils (petroleum), C20-50, hydrotreated neutral

A REACH-registered Group III severely hydrotreated petroleum base stock (CAS 72623-87-1) spanning a C20-50 carbon chain range. Produced by hydrocracking and severe hydrotreatment of neutral petroleum fractions to reduce aromatic and polycyclic-aromatic-hydrocarbon content well below the levels found in conventional (Group I/II) mineral oil, which is why finished lubricants built on this base stock are commonly marketed as "full synthetic" under the API Group III definition.

Toxicology testing on this class of severely refined base oil consistently shows low acute toxicity (oral, dermal, and inhalation LD50/LC50 values well above hazard-classification thresholds) and no adverse skin or eye irritation in standard testing. IARC classifies severely hydrotreated distillate base oils in this category as Group 3, not classifiable as to carcinogenicity to humans, in contrast to unrefined or mildly refined mineral oil fractions, which do carry a Carcinogen Category 1B classification. The ingredient carries an aspiration-hazard (H304) classification at the raw ingredient level, but finished lubricant formulations using this base stock at the high kinematic viscosities typical of ATF and gear oil (generally above 20.5 mm2/s at 40C) qualify for the CLP viscosity exemption, which waives H304 from the mixture-level SDS classification.