Catalytic converter cleaning ranges from $20 (DIY fuel additive) to $400 (professional water-spray or chemical service). It only works on partially clogged or mildly contaminated cats. Severely failed cats must be replaced.
Most drivers pay $25 to $80 at an independent shop. Most owners get the same result with a $25 fuel additive that a shop charges $300 for.
Oil and coolant contamination cannot be cleaned. Carbon buildup can.
Cataclean and Hi-Gear cost $20-$30. Pro services (Mr. Cat Clean, dealer flushes) run $200-$400.
If P0420 returns within 100 miles after cleaning, the cat is mechanically damaged.
Cleaning works best when followed by 30+ minutes of highway driving at 2,500+ RPM.
Cleaning solutions can sometimes resolve a bad oxygen sensor issue.
Cats over 150,000 miles rarely respond to cleaning.
| Vehicle | Typical Range | Notes |
|---|---|---|
| 2008 Honda Accord 2.4L | $25 - $80 | DIY additive most common |
| 2012 Toyota Camry 2.5L | $30 - $100 | DIY first, shop if no improvement |
| 2010 Ford F-150 5.4L | $50 - $250 | multiple cats, dual additive |
| 2014 Chevy Silverado 5.3L | $50 - $250 | larger system |
| 2016 Subaru Outback 2.5L | $30 - $200 | known cat issues - cleaning rarely works long-term |
| 2018 BMW 328i | $80 - $400 | dealer service preferred |
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For partial clogs and light carbon buildup, yes - a tank of Cataclean plus 30 minutes of highway driving can clear P0420. For oil-soaked or melted cats, no.
If the underlying cause (misfire, rich condition, oil burning) is fixed - permanently. If not, expect the code to return in days to weeks.
Yes - most DIY products and shop services work without removing the cat. Soaking a removed cat in cleaning solution is rarely worth the labor.
Sometimes. If the code is from buildup, yes. If the cat substrate is broken or melted, no - replacement is the only fix.
If a replacement cat is $1,000+, trying a $25 cleaner first is always smart. For sub-$300 cats, replacement is the safer bet.
Misfires sending raw fuel through, oil consumption from worn rings, coolant leaks into combustion, or chronic rich-running conditions.