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Washington Exhaust & Muffler Laws (2026)
Info: Your vehicle needs a muffler in good working order, cutouts and bypasses (which route exhaust around the muffler) are prohibited, and so is exhaust amplified beyond the factory muffler.
Your vehicle needs a muffler in good working order, cutouts and bypasses (which route exhaust around the muffler) are prohibited, and so is exhaust amplified beyond the factory muffler. Washington sets no decibel limit in statute (RCW § 46.37.390).
Official source: app.leg.wa.gov →
General legal information, not legal advice — verify important decisions with a licensed attorney.
Exhaust & Muffler in states bordering Washington
The same rule in each neighboring state LawLert has verified, from that state’s own official source.
- IdahoInfo
Your vehicle needs a muffler in good order, and cutouts and bypasses (which route exhaust around the muffler) are banned, along with changes that make the exhaust louder — in Idaho, "excessive noise" means more than 92 decibels measured at 20 feet (Idaho Code §§ 49-937, 49-106).
Verified Jun 19, 2026 · Source: legislature.idaho.gov · Full Idaho rule →
- OregonInfo
Your vehicle needs a proper exhaust. On the Department of Environmental Quality's stationary test, passenger cars built in 1976 or later are capped at 88 decibels, and cars built before 1976 at 92 decibels, measured at 25 feet (Or. Rev. Stat. § 815.250).
Verified Jun 19, 2026 · Source: oregonlegislature.gov · Full Oregon rule →
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