WD-40 Specialist Carb/Throttle Body & Parts Cleaner

All three are aerosol carb cleaners with DANGER signal words and high VOC. The chemistry differs in ways that matter. Berryman B-12 is the aggressive option: methanol, acetone, and toluene blend, widely regarded in small-engine forums as the strongest on severe varnish; community reports describe it as harsher on rubber diaphragms than acetone-only formulas, and it carries a Prop 65 warning. Gumout Carb/Choke is acetone-toluene with H361d reproductive-toxicity Cat 2 and a Prop 65 warning. WD-40 Specialist is the milder profile of the three: acetone-dominant with small fractions of heptane and isopropyl alcohol, NO toluene, NO methanol, NO Prop 65 warning, and NO reproductive-toxicity classification. For throttle body work and rubber-component carbs it's the lower-risk pick; for severe sitting-fuel lacquer on small engines B-12 is still the community go-to.

Yes for external surface cleaning — the formula is one of the more rubber-friendly options in the category since there's no toluene or xylene to attack elastomer plasticizers. Avoid spraying into the intake while the engine is running (the manufacturer page warns against it), and don't soak rubber boots, vacuum hoses, or plastic mass-airflow sensors. For direct-injection systems with carbon-coked intake valves, a dedicated GDI intake valve cleaner is a better tool — this product cleans the throttle plate and butterfly face, not the back side of the intake valves.

Those two facts are both true and not contradictory. CARB compliance is a regulatory accounting result: acetone is exempt from U.S. EPA and CARB consumer-product VOC counting under 40 CFR 51.100(s) because it has very low photochemical ozone reactivity. The formula's absolute solvent fraction is roughly 85–100% by mass — measured solvent emissions are in the 700–800 g/L range. The high_voc flag in CarCareTruth scoring reflects the absolute chemistry, not the regulatory accounting. The label and the SDS are both honest; they're using different VOC definitions.

Short, targeted spray application typically does not damage common carburetor rubber at standard 5–10 minute dwell times. Acetone is a relatively benign solvent for fluoroelastomer O-rings at brief exposure, and the absence of toluene, xylene, and MEK in this formula is the meaningful safety advantage versus Berryman B-12. Avoid pooling the solvent against rubber components and avoid prolonged soaks; for soaking, use a dedicated carb-dip product. ABS plastics and some painted surfaces can craze with prolonged contact — spray, don't drown.

The WD-40 Company SDS for this product was last revised on 2018-08-27 — over seven years old. WD-40 has not publicly hosted a newer revision. The 2018 SDS already claims compliance with current CARB and U.S. EPA consumer-product VOC rules, which suggests the formula did not change in the 2019–2022 reformulation wave that affected other carb cleaners. CarCareTruth's scoring uses the 2018 SDS as the authoritative source while flagging the staleness; if WD-40 issues a revision, the page will be re-scored.