Gold Eagle Co. STA-BIL Carb/Choke & Parts Cleaner

At standard 5–10 minute dwell times community evidence on small-engine and motorcycle forums shows no consistent rubber-damage reports for typical rubber O-rings. Prolonged soak (15+ minutes) or repeated immersion can swell some rubbers — toluene is a known plasticizer-leacher. For assembled carbs with rubber components, spray-and-flush in short bursts and avoid pooling the solvent against gaskets. Skip it on diaphragm carbs (CV-style on Japanese motorcycles) — those rubber diaphragms are particularly sensitive to aromatic solvents.

The manufacturer claim 'Will not harm catalytic convertors or oxygen sensors' is on the listing and label. The acetone-and-toluene chemistry doesn't carry the silicone, phosphorus, or lead compounds that classically poison O2 sensors and three-way catalysts, which supports the claim chemically. For routine throttle-body cleaning on a port-injected engine, this is more aggressive than necessary — Gold Eagle and other brands sell dedicated throttle-body cleaners that are gentler on sensor coatings. For direct-injection systems, use a dedicated GDI intake-valve cleaner instead.

DANGER here is driven by both flammability and health H-codes. SDS §2 lists H222 (extremely flammable aerosol), H224 (extremely flammable liquid and vapor) — physical hazards — alongside H319 (Cat 2 serious eye irritation), H336 (drowsiness or dizziness from vapor inhalation), and H373 (target-organ toxicity through repeated exposure). The flash point of −104 °C and vapor pressure dominated by acetone (185 mmHg) make the flammability classification immediate; H336 and H373 make the inhalation hazard real for enclosed-garage use.

Yes — the operative label warning is for toluene developmental toxicity. Toluene (CAS 108-88-3) is listed under California Prop 65 since 1991, and the mixture contains toluene at 0.1–20% per SDS §3. The Amazon listing flag confirms the warning, even though SDS §15.3 omits the explicit line. The California-market label legally must carry the warning.

All three are aerosol carb cleaners in the same DANGER/Prop 65/high-VOC regulatory band. The STA-BIL formula differs in two SDS-disclosed ways: (1) no H361/H361d reproductive-toxicity classification at the mixture level despite toluene presence — Gumout's same-class formula does carry H361d; (2) SDS §12.1 explicitly states 'not considered harmful to aquatic organisms,' where most carb cleaners carry H411/H412. The 'Safe For Oxygen Sensors' claim is on this label specifically. For routine maintenance on a lawnmower or generator, all three perform comparably; Berryman B-12 remains the small-engine community pick for severe varnish.