"Fuel-Saving Miracle" Exposed as Illegal Modification: Experts Debunk 10 MPG to 40 MPG Scam

A viral video claims that installing an "oxygen sensor spacer" in a vehicle's exhaust system can boost fuel economy from 10 MPG to 40 MPG. However, automotive experts and state inspectors warn that this device is actually a "defeat device" that interferes with oxygen sensor readings, causing the engine control unit to misjudge emissions levels and falsely report improved fuel efficiency. It does not genuinely fix a clogged catalytic converter. More seriously, under the U.S. Clean Air Act, such modifications constitute illegal tampering with emission control systems and can result in fines—even in states without mandatory vehicle inspections. Experts stress that accurate fuel economy should be verified manually by tracking fuel consumption against mileage, and that the only reliable solution to high fuel consumption is professional diagnosis and repair—not online "quick fixes."