Cataclean Complete Engine Cleaner
The best-known catalytic converter and fuel-system cleaner — pour into a low tank and drive to clean deposits that can contribute to a P0420.
- Targets cat + O2 sensors
- Easy pour-in-tank use
- Widely trusted
Engine Repair Parts
Best Catalytic Converter Cleaners for a P0420 Code
The short answer
The best catalytic converter cleaner is a fuel-system additive (such as Cataclean) that you pour into a low tank and drive — it can clean light carbon and sulfur deposits that contribute to a P0420/P0430 code, and is worth trying as a low-cost first step before an expensive converter replacement.
A P0420 (or P0430) "catalyst efficiency below threshold" code does not always mean the converter is dead — sometimes deposits or a lazy oxygen sensor are the culprit. A catalytic converter cleaner is the cheapest first thing to try. Set realistic expectations: it can help a marginal system, but it will not resurrect a physically failed converter.
Wear the code
All merch →Shirts, mugs and garage gear. Printed when you order, free US shipping.
Our top pick, best overall
Cataclean Complete Engine Cleaner
Quick picks at a glance
- Best overall Cataclean Complete Engine Cleaner Check price
- Best value CRC Catalytic Converter Cleaner Check price
What to look for
- Designed to clean the catalyst and O2 sensors via the fuel system.
- Correct dosing for your tank size, used on a low tank then driven at highway speed.
- Reputable brand with consistent results (e.g. Cataclean, CRC).
- Realistic expectations — additives help marginal systems, not a physically failed converter.
- Pair with fixing the root cause (misfire, oil burning, leaking O2 sensor) so the code does not return.
Our picks
CRC Catalytic Converter Cleaner
A budget-friendly fuel-system cleaner formulated to help clean the catalyst and reduce deposits — a low-cost first attempt at a P0420.
- Cleans fuel system + cat
- Affordable
- Simple pour-in
Frequently asked questions
Do catalytic converter cleaners actually work?
They can help when the converter is marginal or the code stems from deposits or a slightly lazy oxygen sensor. They will not fix a physically failed or clogged converter. As a low-cost first step before replacement, they are worth trying — especially after fixing the underlying cause.
How do I use a catalytic converter cleaner for a P0420 code?
Pour the recommended dose into a low fuel tank, then drive at highway speed for a sustained period to get the exhaust hot and let the additive work. Clear the code afterward and see whether it returns over the next few drive cycles.
What if the cleaner does not clear my P0420?
If the code returns, diagnose the root cause: a failing downstream oxygen sensor, an exhaust leak, a misfire, or oil consumption can all trigger P0420. The converter itself may need replacement if it has physically degraded.
Diagnose it first with AXLY.pro — free
AXLY.pro is a free iPhone app that pairs with any Bluetooth OBD2 adapter to read codes, watch live engine data, and time your runs — so you fix the right thing before you buy parts.
As an Amazon Associate, AXLY earns from qualifying purchases — at no additional cost to you. Links to Amazon on this page are affiliate links. Links to the AXLY shop are our own products, which we make and sell ourselves. We only recommend things we would use.
Top pick: Cataclean Complete Engine Cleaner Check price