CarCareTruth Score
Mediocre, 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.
GHS Category 1 germ-cell mutagenicity — classified as suspected of causing heritable genetic damage.
GHS Category 1 carcinogenicity — classified as suspected of causing cancer with repeated or prolonged exposure.
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: splash risk
Beyond SDS: translated from the ingredient chemistry
No H319 or H318 in SDS §2 mixture-level classification, but the volatile aromatic-carrier basket at concentrate strength is a credible eye-splash hazard during the narrow-fill-neck pour.
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
Translated from the manufacturer’s Safety Data Sheet, Section 2
H315 (skin irritation) present in SDS §2; brief, accidental drip contact is the realistic exposure during a fuel-tank pour.
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.
Beyond SDS: translated from the ingredient chemistry
SDS §2 carries H332 (acute inhalation Cat 4) plus H336 (narcotic effects), H340 (mutagen Cat 1B), and H350 (carcinogen Cat 1A) · driven by §3 benzene, naphthalene, cumene, and the heavy aromatic/kerosene carrier basket. Editorial escalation to `required` (Beyond SDS) reflects the chronic-hazard chemistry plus the multi-substance Prop 65 listing · not just the §2 H332 acute tier.
U.S. regulatory standard
29 CFR 1910.1000; 1910.1200
“Each employer shall assure that no employee is exposed to an inhalation concentration of any substance shown in Tables Z-1, Z-2, or Z-3 in excess of the limits in the tables.”
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 #15 of 16 in Fuel Injector Cleaner.Three above it ↓
Last reviewed July 31, 2026
TL;DR The active detergent is a Mannich-class polyolefin alkyl phenol alkyl amine at 1-<5%wt · named in the SDS but well below the functional threshold for the PEA gold-standard chemistry, and with no independent SAE or dyno test data. Health score 4.0 (Serious Hazard band): DANGER signal word driven by carcinogen Cat 1A, mutagen Cat 1B, aspiration hazard, and narcotic effects, plus a multi-substance Prop 65 warning and a heavy petroleum-distillate carrier. **Do not induce vomiting if ingested · seek medical attention.**
The active is a Mannich-class detergent · a nitrogen-containing fuel-soluble compound that targets injector and combustion-chamber deposits. It is not the polyetheramine chemistry that the most-studied independent research evaluates, and at 1-<5%wt it sits below the concentration range where the rubric treats a named active as "functional." The brand states the product unclogs dirty injectors and treats up to 21 gallons per bottle; community evidence on BITOG positions STP as a value/maintenance option rather than a deep-clean treatment, and there is no SAE paper or independent dyno test specific to this product. Protocol is one bottle every oil change or 4,000 miles.
Best fit for gasoline owners who run non-Top-Tier fuel and want a low-cost periodic maintenance dose from a long-standing mass-market brand. Skip it if you always run Top Tier certified gasoline · the OEM detergent package already covers maintenance dosing. Skip it for direct-injection engines with intake-valve carbon symptoms · the tank-route delivery cannot reach GDI intake-valve deposits, and the Mannich detergent class is not positioned for that use. Skip it and seek professional service if symptoms are severe (major rough idle, stalling) · one bottle of consumer treatment is insufficient.
SDS §2 is DANGER · H350 (carcinogen Cat 1A), H340 (mutagen Cat 1B), H361fd (suspected reproductive toxin), H304 (aspiration hazard), H332 (acute inhalation Cat 4), H336 (narcotic vapour effects), H315 (skin irritation), and H226 (flammable liquid). The product listing carries a Prop 65 warning, and SDS §15 names benzene, ethylbenzene, naphthalene, toluene, and cumene as Prop 65 listed substances at trace concentrations in the carrier basket. Lungs tier is required (Beyond SDS) reflecting the chronic-hazard chemistry rather than the acute §2 H332 alone. Do not induce vomiting if ingested · seek medical attention. The product combusts in the engine; exhaust byproducts are the environmental endpoint.
The listing for STP Super Concentrated Fuel Injector Cleaner carries a California Prop 65 warning. STP Super Concentrated Fuel Injector Cleaner is a working automotive fluid rather than a passive part, so the warning points at the formulation itself. The manufacturer's Safety Data Sheet is the primary source for what is in it: the hazard classification and the PPE tiers on this page are translated from that sheet, and the full SDS is linked from the safety panel. California requires the warning whenever exposure to any of roughly 900 listed substances is possible. It does not name which substance applies to a given product, and it states no dose or risk level, so it is not on its own a measure of how hazardous this fluid is in normal use.
Marketing copy from STP, via Amazon. Not editorial.
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