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 #10 of 16 in Fuel Injector Cleaner.Three above it ↓
Last reviewed June 28, 2026
TL;DR DANGER signal word and H318 serious eye damage · can cause permanent injury: wear safety goggles when pouring. PEA chemistry confirmed from the US SDS, credibly targeting injectors and intake valves; combustion-chamber coverage is the brand's claim only. Well-reviewed by owners, with a broadly positive reputation.
STP Ultra 5-in-1 uses polyetheramine (PEA) · the detergent class with the most independent research on injector and intake valve deposit removal · confirmed directly from the US SDS. Co-active chemistry the brand doesn't publicly name covers combustion chambers, according to the manufacturer. One 12 oz bottle treats up to 35 gallons; pour the full bottle into a tank that's at least half-full, every 4,000 miles. Community ratings are broadly positive and the product is well-reviewed by a large owner base; no SAE paper or independent dyno test found for this specific product.
Best for gasoline-engine owners who run non-Top Tier certified fuel and want a maintenance dose of confirmed PEA chemistry on a 4,000-mile schedule. Skip it if you consistently run Top Tier gasoline · that OEM detergent package already handles prevention. Skip it for misfires, rough idle, or confirmed injector failure beyond typical deposit buildup · a pour-in product is not a substitute for professional ultrasonic cleaning.
DANGER signal word driven by H304 (aspiration hazard Cat 1) and H318 (serious eye damage Cat 1 · permanent injury risk). Do not induce vomiting if ingested · seek medical attention. Wear safety goggles; skin contact warrants nitrile gloves given the H317 skin sensitizer classification. The product combusts in the engine · exhaust byproducts are the environmental endpoint.
Marketing copy from STP, via Amazon. Not editorial.
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