Auto Clip Notes

20‑Minute Fix: Clean Your Catalytic Converter and Erase P0420 Codes

A quick, low‑cost, high‑impact automotive maintenance recipe that cleans your catalytic converter in just 20 minutes. Using a simple fuel additive and a short highway drive, you can restore engine performance, clear P0420 codes, and save thousands of dollars on a replacement.

Ownership & Maintenance
May 8, 2026

Table of Contents

Description

Imagine a dish that revives your car’s heart with minimal effort and a tiny budget. This recipe is a quick, low‑cost, high‑impact automotive maintenance routine that cleans your catalytic converter in just 20 minutes. By combining a fuel‑borne cleaner with a short, sustained highway drive, you can restore engine performance, clear P0420 codes, and avoid a costly replacement.

Ingredients

  • 1 bottle (16 oz) of catalytic converter cleaner (e.g., Catleen, Techron, or a similar product) – about $20
  • 1/4 full fuel tank of gasoline (approximately 4 gal) – use premium if your vehicle recommends it
  • Optional: OBD2 code reader to clear diagnostic trouble codes

Instructions

  1. Prep the tank. Park your vehicle on a level surface and ensure the engine is off. If your tank is more than 3 gal full, add a small amount of gasoline to bring it to roughly 1/4 full (about 4 gal remaining).
  2. Pour the cleaner. Open the fuel cap and pour the entire bottle of catalytic converter cleaner into the tank. The cleaner will mix with the gasoline and travel through the engine to the exhaust.
  3. Top off. Fill the rest of the tank with gasoline, using a quality brand if possible. Premium fuel can help keep the combustion chamber cleaner.
  4. Drive to a safe stretch of highway. Find a road where you can maintain a steady speed without frequent stops or traffic lights.
  5. Maintain engine speed. Keep the engine RPM between 2,500 and 3,000 for at least 20 continuous minutes. If your car cruises at 65 mph in a high gear, downshift or use sport mode to hit the target RPM. The goal is to raise the exhaust temperature into the 800–1,800 °F range where the cleaner’s chemicals can dissolve carbon deposits.
  6. Finish the drive. After the 20‑minute run, continue driving normally until the tank is nearly empty. This ensures the cleaner is fully burned and the catalyst is flushed.
  7. Optional: Clear codes. If you have an OBD2 scanner, connect it and clear any stored P0420 or related codes. Allow the car to run a few more cycles to confirm the codes remain off.
  8. Repeat as needed. For preventive maintenance, repeat this process every 3–4 months or every 5,000 mi, especially if you drive mostly in city traffic.

Optional

Tips & Notes

  • Check engine health first. Ensure spark plugs, air filter, and oxygen sensors are in good condition. A misfiring engine can send unburned fuel into the converter, causing damage.
  • Use quality fuel. Switching to a top‑tier brand with higher detergent additives can keep the fuel system cleaner and support the cleaning process.
  • Watch for a mild sulfur smell. After the run, you may notice a slightly sulfurous odor from the exhaust. This is normal and indicates the cleaner is working.
  • Know when it won’t work. If the converter’s ceramic honeycomb is melted or cracked, cleaning will not help. In that case, replacement is necessary.
  • Safety first. Keep the vehicle in a well‑ventilated area during the drive, and avoid driving in extreme weather that could affect engine performance.

Prep Time: 5 min
Drive Time: 20 min
Total Time: 25 min

This simple, low‑cost recipe can save you thousands of dollars and keep your vehicle running smoothly. Give it a try the next time your check‑engine light comes on or you notice sluggish acceleration.

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