Petroleum Distillates, Hydrotreated Light

What it is

Hydrotreated light petroleum distillate (CAS 64742-47-8) is a refined petroleum stream produced by hydrotreating straight-run middle distillate over a catalyst at high temperature and pressure. The hydrotreating step pushes hydrogen through the feedstock to strip sulfur (typically to below 15 ppm), nitrogen, and most aromatic ring compounds. The finished cut typically contains less than 0.1% benzene and total aromatics below 5%. Boiling range runs roughly 150 to 300°C, with viscosity in the 1 to 3 cSt range. The resulting liquid is a clear, low-odor aliphatic hydrocarbon mixture, dominated by branched and straight-chain paraffins with some naphthenes.

Why "hydrotreated" matters

The unhydrotreated equivalent (CAS 64742-88-7, "solvent naphtha medium aliphatic") carries much higher aromatic content and a correspondingly higher H304 aspiration concern driven by the aromatic fraction, along with measurable benzene content that places it on California Prop 65. Hydrotreating is the processing step that turns the same petroleum cut into a stream acceptable for consumer-facing products. Two cuts with similar boiling ranges can have very different hazard profiles depending on whether the hydrotreating step was applied.

Where it appears in car care

This is the single most common solvent base in the CCT catalog. It shows up in penetrating oils, lubricant carrier fluids, tire shine vehicles, multi-surface protectants, fuel system cleaners as a solvent base, engine degreasers, wax and oil removers, and undercoatings. The reason for its prevalence is a combination of low cost, low aromatic content compared to alternatives, and a slow enough evaporation rate to keep an active in contact with the substrate long enough to do its work.

The H304 classification

H304 ("may be fatal if swallowed and enters airways") is the headline hazard on the SDS for this material. The mechanism is aspiration pneumonia: the low viscosity of the liquid allows it to pass the epiglottis and reach the lungs if a swallowed dose is vomited back up. Once in the lung tissue, the hydrocarbon causes chemical pneumonitis. This is a different pathway from oral toxicity. Small swallows are passed through the gut with minimal systemic absorption, and the LD50 oral rat is generally above 5000 mg/kg, placing it in the low acute toxicity bracket for ingestion. The aspiration pathway is the reason most consumer products carrying this chemical ship in dispense-controlled containers such as trigger sprayers and aerosol cans rather than open-pour jugs.

Other typical hazards

H315 (skin irritation) appears with prolonged or repeated contact, driven by the defatting action of aliphatic solvents on skin lipids. H336 (drowsiness or dizziness) shows up with high vapor exposure in poorly ventilated spaces. H401 or H411 (aquatic toxicity, acute or chronic) appear on a formulation-dependent basis, sometimes as HNOC or "Other Information" SDS entries rather than formal classification.

Regulatory status

Not listed on California Prop 65, because hydrotreating strips the benzene that places the unhydrotreated equivalent on the list. Classified as a volatile organic compound under most US air-quality rules; the federal VOC definition exempts only specific compounds and this stream is not among them. Not classified as an asthmagen by AOEC or other occupational health bodies.

Environmental profile

Not readily biodegradable on the OECD 301F 28-day timeframe. Water solubility is low, and bioaccumulation potential is low to moderate depending on the specific carbon-chain distribution. In a spill scenario, the dominant fate is evaporation to the atmosphere rather than soil penetration or groundwater migration. The "persistent" environmental flag on this ingredient page reflects the slow biodegradation rather than long-range transport.

What to look for on the SDS

Section 3 (Composition) often lists this material by CAS number with a concentration range such as "30 to 60%" rather than by name. Common synonyms include "Stoddard solvent," "white spirit," "aliphatic hydrocarbon solvent," and "mineral spirits." Section 9 (Physical and Chemical Properties) typically shows a flash point in the 38 to 65°C range, which places the material in the Class 3 flammable liquid category for transport classification. Section 11 (Toxicological Information) carries the LD50 oral rat above 5000 mg/kg, but the H304 aspiration entry under the hazard statements is the real driver of the headline warning.