Aftermarket Exhaust in Oregon
Replacing the exhaust system is legal in Oregon, but a muffler in good working order is required and cutouts or bypasses are prohibited. There is no statutory 'no louder than stock' rule — the standard is that the exhaust must not produce excessive or unusual noise.
Verified against primary sources · August 2026
What the law says
Replacing the exhaust system is legal in Oregon, but a muffler in good working order is required and cutouts or bypasses are prohibited. There is no statutory 'no louder than stock' rule — the standard is that the exhaust must not produce excessive or unusual noise. Removing the catalytic converter is prohibited by federal law (Clean Air Act § 203) regardless of state rules. Oregon DEQ sets limits of 94 dBA for pre-1976 vehicles and 91 dBA for 1976 and newer, with exemptions for special-interest, street rod, and antique vehicles. DEQ emissions testing applies in the Portland and Medford areas.
Specific Limits
- Cutouts
- prohibited
- Muffler required
- Yes
- Louder than stock
- not addressed; excessive noise standard applies
- Catalytic converter
- removal prohibited by federal law
Frequently Asked Questions
Are aftermarket exhaust legal in Oregon?
What are the exact aftermarket exhaust limits in Oregon?
Street-legal aftermarket exhaust picks
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