CarCareTruth Score
Decent.
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Prices may varyHealth 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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From the manufacturer’s Safety Data Sheet, Section 8
“SDS §2 lists H320 (eye irritation Cat 2B, reversible within 7 days, no GHS pictogram required). SDS §8 directs protective glasses or safety goggles where splashing or spray-back is likely. Spraying the concentrate or working solution into an engine bay at face height is the documented spray-back scenario.”
— Simple Green
U.S. regulatory standard
29 CFR 1910.133(a)(1)
“appropriate eye or face protection when exposed to eye or face hazards from… liquid chemicals…”
ANSI Z87.1 (incorporated via §1910.6)
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.
From the manufacturer’s Safety Data Sheet, Section 8
“No H315 skin irritation code at mixture level. SDS §8 directs impervious gloves for prolonged or repeated contact and for concentrate handling, citing the alkaline pH (10-11.5). Short spray-and-rinse sessions at working dilution do not trigger the skin tier; concentrate handling and extended commercial exposure do.”
— Simple Green
CarCareTruth publishes the cited sources verbatim and does not advise what action a user should take. Consult the full SDS before use.
From the manufacturer’s Safety Data Sheet, Section 8
“No respiratory H-code at mixture level (no H334, H335, or H331). VOC is 20 g/L, well below the high-VOC threshold. The enclosed_space trigger captures the engine-bay spray scenario where mist accumulates in a closed garage; outdoor or open-garage use does not require respiratory protection.”
— Simple Green
CarCareTruth publishes the cited sources verbatim and does not advise what action a user should take. Consult the full SDS before use.
No PPE specified in published sources for ventilation. Absence does not imply “not needed” — consult the full Safety Data Sheet.
PPE tiers translate the manufacturer’s SDS and U.S. regulatory standards. Not professional safety advice. How we report safety.
This product ranks #4 of 11 in Engine Degreaser.Three above it ↓
Last reviewed June 14, 2026
TL;DR Heavy-duty alkaline concentrate, a step up from the regular green Simple Green. WARNING signal word with one mild eye-irritation classification, biodegradable per a 94%/28-day label claim, CARB-compliant at 20 g/L VOC. The Prop 65 warning is real but driven by a trace ingredient at less than 0.01% concentration. Safety glasses for spraying, gloves when handling the concentrate.
Pro HD is the purple-cap professional sibling to the regular green Simple Green: same brand, distinctly stronger chemistry. Alkaline-based with a phosphate-and-silicate builder system, built to cut grease the regular green formula leaves behind. Label dilutions: 1:3 heavy, 1:5 medium, 1:10 light. For a typical neglected engine bay, start at 1:5 and step up to 1:3 only if the first pass leaves deposits. Spray onto cool surfaces, dwell, agitate with a brush, rinse. Do not let the solution dry. A corrosion inhibitor is designed into the formula, which is why the label can claim non-corrosive to metals and safe on aluminum.
The right call for tough engine-bay grease, baked-on oil, or heavy-duty cleaning where the regular green Simple Green is not cutting it. Skip Pro HD if you want the milder original Simple Green Industrial Cleaner, which has no GHS classification and no Prop 65 warning. Also skip it for leather, suede, asphalt, painted markings, or prolonged contact on coated paint at full concentrate.
The SDS (Version 13421-24A, June 2024) carries a WARNING signal word with one hazard statement: "Causes Eye Irritation," Eye Irritant Category 2B (reversible within 7 days, no pictogram required). No skin, respiratory, carcinogenicity, or reproductive H-codes at the mixture level. The Prop 65 warning is driven by a trace pH co-buffer at less than 0.01% concentration; California law requires the warning at any detectable amount, which is why this product carries a Prop 65 hazard label on the site. PPE the SDS directs: safety glasses for spraying; nitrile gloves for handling concentrate or prolonged repeated contact (SDS §8). No respirator under normal home use: no inhalation H-codes, 20 g/L VOC, and the glycol-ether solvent here has a cleaner inhalation profile than the 2-butoxyethanol common in this category. Environmental profile is unusually clean for a heavy-duty degreaser: CARB-compliant, no aquatic-toxicity classification, label-confirmed biodegradation (94% in 28 days). SDS §14 lists "Marine Pollutant: NO." Rinse onto grass or soil where possible; engine-bay runoff carries motor oil regardless of the degreaser's profile.
No, they are different formulas with different chemistries. Regular Simple Green Industrial Cleaner & Degreaser (the green one) carries no GHS classification, has 0 g/L VOC, pH 8.5-9.5, and is EPA Safer Choice certified. Pro HD (purple cap) is the heavier-duty sibling: WARNING signal word, Eye Irritant Cat 2B classification, pH 10-11.5, 20 g/L VOC, carries a Prop 65 warning, and is not on the EPA Safer Choice list. Use Pro HD when regular Simple Green is not cutting tough engine-bay grease; use regular Simple Green for milder cleaning jobs where the lower hazard profile is worth the trade-off in cutting power.
Simple Green's label dilution chart: 1 part Pro HD to 3 parts water (1:3) for heavy cleaning, 1:5 for medium, and 1:10 for light. For typical engine-bay grease, start at 1:5 and adjust toward 1:3 only if the first pass leaves deposits. A 1-gallon concentrate yields up to 11 gallons of working solution at the 1:10 light-duty ratio (1 gallon concentrate plus 10 gallons water), or 6 gallons at 1:5, or 4 gallons at 1:3. Spot-test on a hidden area first; do not allow the solution to dry on any surface.
The Pro HD formula contains a trace pH co-buffer at less than 0.01% concentration that is on California's Proposition 65 list as a carcinogen. California law requires the warning at any detectable concentration. The Prop 65 warning is mandated by the trace ingredient; it is not a statement about the overall product hazard level, and the SDS classifies the mixture-level hazard as eye irritation only.
Per the product label: non-corrosive to metals (including aluminum), non-degrading to plastics, and clean-rinsing, formulated with a corrosion inhibitor specifically for metal-cleaning applications. The label specifically warns NOT to use on suede, leather, asphalt, unfinished wood, opals, pearls, or painted markings. At full concentrate, the alkaline pH (10-11.5) can strip wax and sealant on coated paint, so avoid prolonged contact on finished body panels.
Yes, biodegradable per the product label's quantitative claim of 94% biodegradation within 28 days after disposal into a typical sanitary sewer or septic system (an OECD 301D-equivalent claim). SDS §14 lists 'Marine Pollutant: NO.' That said, every drain-destined automotive degreaser should ideally be rinsed onto pervious surfaces (grass, soil) rather than directly into storm drains, because the runoff carries dissolved motor oil and other engine-bay residue regardless of the degreaser's own biodegradability.
Marketing copy from Simple Green, via Amazon. Not editorial.
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