Simple Green Pro HD Heavy-Duty Cleaner & Degreaser

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 — 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 exceed 1:10 working strength on painted surfaces and do not allow the solution to dry on any surface.

The Pro HD formula contains diethanolamine (DEA, CAS 111-42-2) at less than 0.01% as a trace pH co-buffer. DEA is on California's Proposition 65 list as a carcinogen, which legally requires the warning at any detectable concentration. The Prop 65 warning is mandated by California law for the trace ingredient — it is not a statement about overall product hazard, 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/jewelry/instrument panels. 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 §2 does not classify the mixture for aquatic toxicity, and 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.