Mouse Milk Penetrating Oil
Priced as of May 29, 2026
4.8(424 ratings)Buy on AmazonSaved to your guest loadout. Sign up to also save to your Cabinet (consumables) or Kit (tools you own).
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Prices may varySerious hazard — read before use
The manufacturer's Safety Data Sheet classifies this product with one or more GHS Category 1 health hazards — the most severe tier. The hazard statements in quotes below are the verbatim GHS language from the SDS, as required by OSHA's Hazard Communication Standard. The line under each statement translates the GHS classification into plain language.
- H304 “May be fatal if swallowed and enters airways.”
GHS Category 1 aspiration toxicity — thin, oily liquids can slip into the lungs if swallowed, causing chemical pneumonia.
- H350 “May cause cancer.”
GHS Category 1 carcinogenicity — classified as suspected of causing cancer with repeated or prolonged exposure.
If swallowed, inhaled, or splashed in eyes:
Call Poison Control immediately at 1-800-222-1222 (US, 24/7, free) and have the product container with you. Poison Control's standing guidance is to not induce vomiting after chemical exposure; they will direct first-aid steps based on the specific product.
About this product's hazards. This product's Safety Data Sheet uses signal word danger. Read the manufacturer's SDS and follow all safety instructions before use. CarCareTruth ratings translate the manufacturer's safety sheet. They do not replace the SDS or substitute for a hazard assessment specific to your task.
Health score is for adult use as intended, per the manufacturer's SDS. It does not model child ingestion, accidental spill cleanup, or off-label use. See the safety panel below for full hazard classification, and /disclaimer for the full editorial scope.
From the Safety Data Sheet
Full SDS ↗ (rev. 2021-09-14)GHS hazard codes are quoted from the manufacturer’s Safety Data Sheet. PPE tiers below translate those codes and the listed ingredient chemistry; they are not CarCareTruth recommendations.
EyesRecommendedMfr. SDS §8 · 29 CFR 1910.133(a)(1) · GHS H319SkinRecommendedMfr. SDS §8 · 29 CFR 1910.138(a) · GHS H315LungsRecommendedMfr. SDS §8 · 29 CFR 1910.1003 · GHS H350Ventilation—No PPE in published sourcesShow details for all categories ▾Hide details ▴
From the manufacturer’s Safety Data Sheet, Section 8
“H319 (Serious eye irritation Cat 2) confirmed in SDS §2 mixture classification — eyes tier escalates to `recommended` per rubric H-code mapping.”
— Mouse Milk
U.S. regulatory standard
29 CFR 1910.133(a)(1)
“The employer shall ensure that each affected employee uses appropriate eye or face protection when exposed to eye or face hazards from… liquid chemicals…”
ANSI Z87.1 (incorporated via §1910.6)
OSHA standards apply to workplaces. Cited here as the U.S. reference threshold for the underlying hazard class.
CarCareTruth publishes the cited sources verbatim and does not advise what action a user should take. Consult the full SDS before use.
From the manufacturer’s Safety Data Sheet, Section 8
“H315 (Skin irritation Cat 2) in SDS §2 mixture classification. Drip-bottle application involves repeated handling near rusted fasteners with potential skin contact; rubric escalates H315 with repeated-contact scenarios to `recommended`.”
— Mouse Milk
U.S. regulatory standard
29 CFR 1910.138(a)
“appropriate hand protection when employees' hands are exposed to hazards such as those from… chemicals which produce an adverse effect on the skin or eyes…”
OSHA standards apply to workplaces. Cited here as the U.S. reference threshold for the underlying hazard class.
CarCareTruth publishes the cited sources verbatim and does not advise what action a user should take. Consult the full SDS before use.
From the manufacturer’s Safety Data Sheet, Section 8
“H332 (Acute Tox. Inhalation Cat 4, 'Harmful if inhaled') confirmed in SDS §2 mixture classification — maps to lungs `recommended` per rubric. H332 is Cat 4 (harmful), NOT H331 Cat 3 (toxic), so the tier does not escalate to `required`. H335 is absent from §2. H336 (STOT SE Cat 3 narcotic effects) is present but H336 does not escalate lungs PPE — it is a CNS hazard, not a respiratory irritant.”
— Mouse Milk
U.S. regulatory standard
29 CFR 1910.1003; substance-specific 1910.1001–1910.1052
“Each employer shall ensure that no employee is exposed [in excess of the substance-specific PEL]…”
OSHA standards apply to workplaces. Cited here as the U.S. reference threshold for the underlying hazard class.
CarCareTruth publishes the cited sources verbatim and does not advise what action a user should take. Consult the full SDS before use.
The published Safety Data Sheet for this product does not specify ventilation protection for consumer use.
Workplace context
29 CFR 1910.134(a); 1910.1000
“the primary objective shall be to prevent atmospheric contamination [via] accepted engineering control measures (for example, enclosure or confinement of the operation, general and local ventilation…).”
Triggered by GHS H336 on the SDS.
OSHA standards apply to workplaces. Cited here as the U.S. reference threshold for the underlying hazard class.
PPE tiers translate the manufacturer’s SDS and U.S. regulatory standards. Not professional safety advice. How we report safety.
The Podium · Top 3 in Penetrating Oil / Multi-Purpose Lubricant
See the full ranking →This product ranks #12 of 14 in Penetrating Oil / Multi-Purpose Lubricant.Three above it ↓
CarCareTruth's Analysis
Last reviewed May 30, 2026
TL;DR DANGER-rated drip-bottle penetrant with a California Prop 65 warning for cancer and reproductive harm; do not induce vomiting if swallowed. Long the default fix in piston-aircraft maintenance for seized exhaust studs and control cables, with a thin formula that wicks into blind threads.
What it is and how it performs
Mouse Milk is drip-applied from an 8 oz bottle, not sprayed. Tip onto the fastener, wait 5–20 minutes, then try to turn it. Aviation-maintenance forums (Pilots of America, BeechTalk, Vans Air Force) have used it for stuck exhaust studs and control-cable terminals since 2018, and Amazon verified-purchase reviewers (4.8 stars across 424 reviews) report success where lighter penetrants stalled. A light oil film remains, but no rust inhibitor is disclosed, so re-seizure protection is modest.
Who should buy this — and who should skip it
The aviation reputation is real, and the drip format places product precisely on a seized fastener without overspray. The Cat 1A carcinogen and Aspiration Hazard Cat 1 classifications, plus the Prop 65 warning, are a meaningful chemistry trade-off for frequent application; a pump-spray or biobased penetrant without those hazards is a lower-cumulative-exposure category fit there. The Amazon listing blocks California shipping outright because the 394 g/L VOC exceeds the CARB penetrant limit.
Safety and environmental impact
The DANGER signal word is driven by the Cat 1A carcinogen and aspiration hazard, both confirmed in SDS Section 2. SDS Section 15 lists toluene and methyl isobutyl ketone as Prop 65 substances. Flash point of 4°C — keep away from ignition sources. Aromatic-petroleum carrier, mixture-level aquatic chronic toxicity, VOC 394 g/L in SDS Section 9. Not CARB-compliant.
Frequently asked questions
Is Mouse Milk Penetrating Oil safe to use?▾
The Safety Data Sheet for Mouse Milk Penetrating Oil carries a DANGER signal word, with classified hazards including H225 (highly flammable liquid and vapour); H304 (may be fatal if swallowed and enters airways); H315 (causes skin irritation). The Amazon listing also carries a California Prop 65 warning. See the PPE breakdown above for use-case-specific guidance translated from the SDS hazard codes.
How does Mouse Milk Penetrating Oil score on CarCareTruth?▾
CarCareTruth scores Mouse Milk Penetrating Oil at 5.4 out of 10 on the composite CCT score, with a health sub-score of 1.0/10. The CCT score blends real-world effectiveness, ingredient health impact pulled from the manufacturer's safety sheet, and environmental footprint against a published category rubric. See the methodology link on this page for the full scoring breakdown.
What's in Mouse Milk Penetrating Oil?▾
Per the Safety Data Sheet ingredient disclosure: SDS §3 (rev. 2021-09-14): Petroleum distillates, hydrotreated light naphthenic (CAS 64742-53-6) 50–60%; Toluene (CAS 108-88-3) 30–40%; Isopropyl Alcohol (CAS 67-63-0) 1–10%; Methylisobutyl ketone (CAS 108-10-1) 1–5%.
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