CarCareTruth Score
Decent, but it's tough on the environment.
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Prices may varyThe 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.
GHS Category 1 aspiration toxicity — thin, oily liquids can slip into the lungs if swallowed, causing chemical pneumonia.
If swallowed:
The aspiration hazard (H304) is about the liquid being swallowed and reaching the airway, not about breathing fumes during normal use.
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.
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.
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Only when: when spraying
Translated from the manufacturer’s Safety Data Sheet, Section 2
No H319 or H318 in SDS §2 mixture classification. Aerosol form factor is the exposure trigger · fine mist near face during spray application.
CarCareTruth publishes the cited sources verbatim and does not advise what action a user should take. Consult the full SDS before use.
Only when: splash risk · prolonged use
Translated from the manufacturer’s Safety Data Sheet, Section 8
SDS Section 8 names neoprene or nitrile gloves and suitable protective clothing. Section 2 carries no skin-hazard GHS code (no H314, H315, or H317), and Section 11 reports no skin irritation under normal conditions, so this is a splash/prolonged-contact precaution rather than a mixture-level skin hazard.
CarCareTruth publishes the cited sources verbatim and does not advise what action a user should take. Consult the full SDS before use.
Only when: when spraying · in enclosed space
Translated from the manufacturer’s Safety Data Sheet, Section 2
H335 is absent from SDS §2 mixture classification. H336 (narcotic effects, STOT SE Cat 3) is present in §2 but H336 is CNS narcosis · not a respiratory irritant · and does not escalate lungs PPE above the aerosol baseline. Aerosol mist in enclosed spaces is the inhalation exposure trigger.
U.S. regulatory standard
29 CFR 1910.1200(f); 1910.132(d)
“The employer shall assess the workplace to determine if hazards are present, or are likely to be present, which necessitate the use of personal protective equipment.”
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.
Scope of these PPE tiers. The tiers on this page translate the product's Safety Data Sheet where one is published, plus its ingredient chemistry, into a comparable rating. They describe a formulation, not a situation: a tier is not a safety determination for any specific user, task, quantity, or environment. The manufacturer's label and use instructions govern how the product is handled. Where the product is used at work, the employer's PPE program and hazard assessment under 29 CFR 1910.132 decide what protection is selected, not this page.
No warranties. CarCareTruth makes no warranties, express or implied, and expressly disclaims the implied warranties of merchantability and fitness for a particular purpose.
This product ranks #22 of 24 in Penetrating Oil / Multi-Purpose Lubricant.Three above it ↓
Last reviewed June 14, 2026
TL;DR DANGER-rated aerosol with a Prop 65 warning for cancer and reproductive toxicity · aspiration hazard if swallowed; do not induce vomiting. Works on moderate rust in 2-4 minutes; heavier corrosion may require an overnight soak. Aerosol mist in enclosed spaces is the primary inhalation concern.
CRC Screwloose wicks a thin formula into corroded threads to break rust's grip on seized fasteners. Owners broadly confirm consistent results on light-to-moderate rust · 2-4 minutes dwell on moderate corrosion; heavily rusted hardware may need a longer soak. The aerosol straw reaches tight clearances and blind bores. Paraffinic oil fractions leave a light residual film, but no dedicated corrosion inhibitor package is disclosed · re-seizure protection is modest.
A practical choice for homeowners or occasional mechanics dealing with a stuck fastener, particularly where plastic components are involved (formula is marketed as plastic-safe). Skip it for regular enclosed-space use · DANGER classification and a confirmed Prop 65 warning compound with repeated aerosol exposure.
DANGER is driven by an aspiration hazard if swallowed · do not induce vomiting if ingested; seek medical attention. Prop 65 warning for cancer and reproductive toxicity confirmed in SDS §15 and on the product label (the product listing false negative; overridden from SDS and label). No H335 in mixture classification; aerosol mist in enclosed spaces is the inhalation trigger. Environmental: petroleum-distillate carrier, two bioaccumulative ingredients, H411 at mixture level, EPA-basis VOC ~797 g/L. CARB-compliant for all 50 states per SDS §15.
The Safety Data Sheet for CRC Screwloose Super Penetrant carries a DANGER signal word, with classified hazards including H222 (extremely flammable aerosol); H336 (may cause drowsiness or dizziness); H304 (may be fatal if swallowed and enters airways). 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.
CarCareTruth scores CRC Screwloose Super Penetrant at 5.5 out of 10 on the composite CCT score, with a health sub-score of 5.0/10. 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.
Per the Safety Data Sheet ingredient disclosure: SDS §3 (rev. 2024-11-19): Distillates (petroleum), hydrotreated light (CAS 64742-47-8) 60-80%; Naphtha (petroleum), hydrotreated heavy (CAS 64742-48-9) 5-10%; 2-Propanol, 1-(1-methyl-2-propoxyethoxy)- (CAS 29911-27-1) 3-7%; Carbon dioxide (CAS 124-38-9) 1-5%; Distillates (petroleum), solvent-dewaxed heavy paraffinic (CAS 64742-65-0) 1-5%; Paraffin oils (petroleum), catalytic dewaxed light (CAS 64742-71-8) 1-5%; Nonane (CAS 111-84-2) 0.1-1.5%; Trade secret…
Marketing copy from CRC, via Amazon. Not editorial.
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