CarCareTruth Score
Mediocre, but wear gloves and ventilate.
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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 2 acute dermal toxicity — classified as toxic in contact with skin.
GHS Category 1 eye damage — classified as causing irreversible eye damage on contact.
GHS Category 2 acute inhalation toxicity — classified as toxic if inhaled.
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.
This product ranks #5 of 5 in Fuel Stabilizer.Three above it ↓
Last reviewed May 26, 2026
TL;DR owners confirm K-100 revives stale fuel after a single off-season · the marine-community use case it was built for. The manufacturer claims 2-year stabilization; community evidence supports single-season protection only. The SDS carries a health-driven DANGER signal word from H331 (toxic if inhaled Cat 3), H318 (serious eye damage), and H370 (organ toxicity), with Prop 65 confirmed for methanol; eye protection and respiratory protection are appropriate for the pour step.
K-100 is a solvent-carrier fuel treatment formulated around 2-butoxyethanol as a phase-separation inhibitor · the chemistry specifically targets the ethanol-blend water absorption problem in E10 and E15 pump gas. A corrosion inhibitor active (cyclic secondary amine, per SDS §3) protects metal fuel system components during extended storage. The manufacturer claims 2-year stabilization; the modest owner reviews base confirms single-season efficacy · marine owners describe reviving a boat engine after sitting all winter on a full tank. Multi-season independent corroboration is thin. Treatment economy is poor: the label directions call for the full 32 oz bottle per tank fill, making it one of the least concentrated options in the category.
Best fit for boat owners and marine users storing gasoline-powered inboard or I/O engines for a winter season · K-100 has a genuine community history in that application and the ethanol co-solvent chemistry addresses the marine E10 problem directly. Also suitable for other seasonal small-engine storage (lawn mowers, generators, motorcycles) with single-season expectations. Skip it if you store fuel for less than a month or two, or if you want strong concentrate economy · the one-bottle-per-tank dose makes it expensive relative to more concentrated alternatives.
These are the GHS classifications from the SDS. The PPE tiers below are translated from these codes and the underlying ingredient chemistry · not from generic SDS Section 8 boilerplate. The SDS assigns DANGER with H331 (toxic if inhaled Cat 3), H318 (serious eye damage Cat 1), H311 (acute dermal toxicity Cat 3), H370 (organ toxicity Cat 1 · visual organ and CNS), and H335 (respiratory irritation). Eye protection is required at the pour step (H318); respiratory protection is recommended for prolonged handling or enclosed spaces (H331). SDS §8 specifies nitrile or butyl gloves and outdoor or well-ventilated conditions. The product is highly flammable (flash point 25.5°C/78°F · H225); keep away from heat, sparks, and open flames. Prop 65 warning is confirmed in SDS §15 for methanol (reproductive toxin). Environmental fate is combustion/exhaust; dispose of unused concentrate through a fuel or chemical recycling program.
K-100 Marine Grade Fuel Treatment addresses three storage problems specific to modern ethanol-blended pump gas: it uses 2-butoxyethanol as a phase-separation inhibitor to prevent water absorption by ethanol, includes a corrosion inhibitor active (per SDS §3) to protect metal fuel system components, and acts as a stabilizer to slow fuel oxidation and gum/varnish buildup during extended storage.
The manufacturer claims stabilization up to 2 years. The owner reviews base is still modest, but owners confirm the product revives stale fuel after a single off-season · owners describe an I/O boat engine that ran perfectly after sitting all winter on a full tank treated with K-100. Multi-season independent corroboration (beyond label restatement) is thin at this ASIN.
The DANGER signal word is driven by health-tier GHS codes in the SDS: H331 (toxic if inhaled Cat 3), H318 (serious eye damage Cat 1), H370 (causes damage to organs · visual organ and CNS, single exposure), and H311 (acute dermal toxicity Cat 3). The formula also carries H225 (highly flammable, flash point 25.5°C/78°F). SDS §8 specifies outdoor or well-ventilated conditions and nitrile or butyl gloves.
Yes · addressing ethanol chemistry is the core brand purpose. The formula includes 2-butoxyethanol (20·40% per SDS §3), a documented ethanol co-solvent that inhibits phase separation. owners confirm use in boats and marine engines running E10 pump gas.
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