Gunk Carb Medic Carburetor & Parts Cleaner (12.5 oz aerosol, M4814)

Carb Medic is built on a different solvent system than the rest of the category. Most modern carb cleaners (CRC #03077, Gumout Jet Spray) are acetone-dominant — acetone is a Class 4 oral-toxicity flag and a Cat 3 narcotic at most, with no carcinogen or reproductive-toxin classifications. Carb Medic uses dichloromethane (methylene chloride) at 60–70% of the formula, plus 10–20% toluene and 10–20% xylene. Dichloromethane is a Prop 65 listed carcinogen, IARC 2A, and an OSHA Specifically Regulated Substance; toluene is a Prop 65 listed developmental toxin and drives the H360 Cat 1A reproductive classification on the mixture. The cumulative result is the H350 + H360 + H370 + H372 + H304 stack that does not appear on any other reviewed carb cleaner.

Methylene chloride has been exempted from the US federal definition of VOC since 1996 under EPA 40 CFR 51.100(s) because it has negligible photochemical reactivity in the atmosphere (it does not contribute to ground-level ozone formation). The SDS Section 9 VOC reading of 44% by weight excludes dichloromethane and computes from toluene, xylene, and ethylbenzene only. Including the 60–70% dichloromethane fraction in the volatile-mass-per-litre accounting gives ~1070 g/L absolute volatile mass — the actual solvent burden in the air when the can is used. The federal exemption is an atmospheric-chemistry decision; it is not a public-health endorsement, and it is independent of dichloromethane's carcinogen and STOT classifications.

Two reasons combine. (1) California's Consumer Products Regulation imposes much tighter VOC limits than the federal accounting, and unlike at the federal level California does not categorically exempt methylene chloride from the consumer-product VOC ceiling for carb cleaners. (2) California Proposition 65 disclosure for dichloromethane (cancer), toluene (developmental), and ethylbenzene (cancer) at the concentrations present here triggers warning obligations that the brand has not retooled the formula to avoid. Gunk does not appear to sell a California-reformulated variant of Carb Medic (unlike the Engine Brite line, which has an EB1CA SKU).

The 2019 TSCA Section 6(h) rule restricted methylene chloride in consumer paint-stripping uses; the SDS Section 1 line 'not and cannot be distributed in commerce ... for consumer paint or coating removal' reflects that rule. The 2024 EPA TSCA Section 6 final rule extends restrictions to most other consumer and commercial dichloromethane uses, with a phased compliance schedule. Carburetor cleaner is not named in either rule's specifically-restricted-uses list, so the product remains legally sold as a carb cleaner. The chemistry profile is shared with applications that have already been restricted, and continued availability is a categorical-scope outcome of the rulemaking rather than a chemistry safety case. As of 2026-05-18 the Amazon listing is 'Currently unavailable' — whether that reflects a commercial decision, a supply-chain interruption, or an anticipatory withdrawal is not publicly documented.

Yes, on heavy varnish. Dichloromethane is a powerful solvent for gum, varnish, and baked-on carbon; the toluene and xylene aromatic fraction extends the cleaning profile. On purely-metal carburetor passages with no assembled rubber, this formula clears deposits more aggressively than acetone-based competitors. Community forum threads from the 2010s reference Carb Medic as a heavy-duty option for sitting-fuel small-engine carbs. The trade-off is the worst chemistry-driven health profile in the category, and modern community guidance (post-2020) routinely steers users toward Berryman B-12 or CRC #03077 first — saving Carb Medic-class chemistry for cases where those have failed.

Dichloromethane attacks most plastics aggressively (polystyrene, polycarbonate, acrylic, ABS, many vinyls, polyurethane), most paints (lifts paint film on contact), and many rubbers (will swell or dissolve NBR/Buna-N O-rings, silicone, many gasket materials). It is non-reactive with metal and most fluoropolymers (PTFE, FKM/Viton). Practical guidance: disassemble before applying. Do not spray onto assembled carburetors with rubber gaskets, plastic linkages, or painted intake components. Brief overspray onto painted engine surfaces will lift the finish.