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.
GHS Category 1 eye damage — classified as causing irreversible eye damage on contact.
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 10 in Fuel System Cleaner.Three above it ↓
Last reviewed July 5, 2026
TL;DR A value-priced whole-system treatment built on a PEA detergent confirmed in the SDS, with PIBA indicated, that credibly reaches injectors and intake valves. The combustion-chamber coverage is a brand claim, not disclosed chemistry. Health 2.45/10 (Severe): a DANGER concentrate with serious-eye-damage and skin-sensitizer classifications plus a Prop 65 warning. Wear eye protection and gloves.
STP Complete Fuel System Cleaner is an inexpensive pour-in treatment positioned to clean the whole fuel system. Its confirmed active is a PEA (polyetheramine) detergent, which credibly cleans fuel injectors and intake valves; the brand also names a PIBA co-active and a temperature-resistant detergent for combustion-chamber deposits, though that combustion-chamber claim has no independent test data behind it. It is a periodic-maintenance dose, not a one-time flush: one 5.25 oz bottle treats up to 15 gallons, at every oil change or 4,000 miles.
Best for owners of port-injected, turbo, or older gasoline engines that have run non-Top-Tier fuel and want an inexpensive routine full-system pour. Skip it if you consistently run Top Tier gasoline, which already carries a detergent package that prevents these deposits. Skip it for severe rough idle, misfires, or injector failure beyond typical carbon fouling, where professional fuel-system service is the right call. Direct-injection owners should treat the intake-valve benefit as unverified.
SDS Section 2 is DANGER, driven by health H-codes: H318 (serious eye damage), H304 (aspiration hazard), H315 (skin irritation), and H317 (allergic skin reaction). Those force eye protection and gloves for the pour; the volatile carrier concentrates little vapor outdoors, but an enclosed garage warrants airflow. Do not induce vomiting if ingested; seek medical attention (H304). The product carries a Prop 65 warning and combusts in the engine, so exhaust byproducts are the environmental endpoint, not wastewater.
The brand describes a two-tier detergent system covering fuel injectors, carburetors, intake valves, cylinder heads, and combustion-chamber deposits. A PEA detergent is confirmed in the US SDS and credibly reaches injectors and intake valves; PIBA is named on the brand page and indicated as a co-active. The combustion-chamber and power-restoration claims are brand assertions with no independent test data on record.
The brand states the product is safe for any gasoline engine, including turbo, direct-injection, and hybrid. That is a compatibility claim, not proof of GDI cleaning: a tank-poured detergent reaches intake valves through the fuel path only on port-injected engines, so a true GDI engine's intake-valve carbon is not fuel-washed. Treat the GDI benefit as compatibility rather than verified cleaning.
The label directs one full 5.25 oz bottle into a full tank (treats up to 15 gallons), used at every oil change or every 4,000 miles. That is a periodic-maintenance dose rather than a one-time high-concentrate flush, so it is best suited to routine upkeep between oil changes.
No documented incompatibility with catalytic converters or fuel injection has been reported, and the brand positions it for the entire fuel system of modern gasoline engines. The brand makes no explicit catalytic-converter statement on this listing, so verify with the manufacturer before use in emissions-critical or warranty-sensitive applications.
The bottle, the Amazon listing, and the brand product page all carry a Prop 65 cancer-and-reproductive-harm warning, even though this SDS revision's Section 15 does not name a specific listed substance. That combination is treated as an active label warning; it most likely reflects a precautionary manufacturer warning tied to a trace aromatic solvent component in the proprietary blend.
Marketing copy from STP, via Amazon. Not editorial.
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