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Cat Complete Fuel, Exhaust & Emissions System Cleaner

  • Turn Off Check Engine Light
  • Clear P0420 & Other OBD Codes
  • Cleans & Restores Catalytic Converter
  • Reduces Emissions, Saves Gas

Innovation in a bottle.

Within one year, this product has become a worldwide bestseller.

Introducing Rislone Cat Complete Fuel, Exhaust & Emission System Cleaner – the most advanced catalytic converter and emissions product available anywhere.

This formula is engineered to help you clean dirty catalytic converters, clear common OBD check engine light (CEL) codes, pass emissions testing and improve the overall health and performance of your fuel system. It’s one of the most advanced formulas we’ve developed in our 100+ year history.

Product Support:

Product Details

Part Number: 4720

Dosage: Add entire bottle into approximately 1/2 full tank car or small to mid-size SUV (1/4 full tank truck or large SUV) of gasoline.

Size: 16.9 FL. OZ. (500 mL)

SDS / Tech Info:
4720 SDS Open Download
Tech Sheet Open Download

Frequently Asked Questions

Additional Product Info

CAT COMPLETE™ Fuel, Exhaust & Emissions System Cleaner has high-performing detergents and heavy duty cleaning solvents that effectively scrub and remove contaminants, soot, carbon build-up, and oily residue from the fuel injectors, combustion chambers, turbo, EGR, catalytic converters, oxygen sensors and the exhaust system. These along with other active chemical agents, react with the gases created in the combustion process to remove the remaining inorganic deposits. This process restores their function and with regular use maintains efficiency.

As fuel is burned contaminating byproducts are created that get circulated throughout various vehicle components. The system is designed to be able to handle this process during most normal engine operation. However, the use of poor quality fuel, short driving distance, cold weather, improper maintenance, and component failure can greatly increase the amount of contamination and deposits created inside these systems. Such factors can cause increased exhaust emissions, reduced fuel economy, lost power & performance, drivability issues, engine overheating, hard starts, check engine light illumination and premature engine wear.


  • Increases power, performance, mileage and saves gas by not only cleaning the entire emissions & exhaust
    system, but the fuel system as well. Works with gasoline, ethanol and hybrid vehicles.
  • Regular use every 5,000 miles tunes-up the fuel, emissions and exhaust systems keeping them clean and
    preventing the CEL light from returning. This also saves on expensive fuel system and emission control repairs.
  • Will not void manufacturer’s new vehicle warranty. Specifically designed and safe to use on vehicles which
    have oxygen sensors and catalytic converters. Exceeds EPA compliance performance criteria.
  • Works on all fuel injected, direct injected, carbureted, turbo, GTDI, Ecotec® & EcoBoost® engines.
  • Clean fuel and exhaust systems reduce excess exhaust hydrocarbon, CO and
    NOX emissions and saves gas.
  • Contains outstanding synthetic detergents to remove (IVD) intake valve
    deposits, (CCD) combustion chamber deposits and other fuel deposits.
  • Includes combustion catalyst for improved gas mileage, smoother idling,
    drivability and better throttle response.
  • Reduces zinc and phosphorus catalyst contamination restoring catalytic
    converter function.
  •  Cleans O2 lambda oxygen sensor tip.
  •  Clear OBD P0420 & other OBD codes* and turn check engine light off.
  •  Deodorizes sulphur “sulfur” (rotten eggs) exhaust smell.
  •  Pass emissions smog test, guaranteed.
  •  50 state legal—EPA registered


Add entire bottle of Fuel, Exhaust & Emissions Systems Cleaner into approximately 1/2 full tank car (1/4 full tank truck) of gasoline. Drive vehicle 20 to 30 miles (ideally half of these miles at highway speeds), and then fill up tank. Continue to drive vehicle normally until below 1/4 tank before refueling. Take emissions test at this time (if needed) and CEL light should be off. Depending on the severity and length of time light has been on, it may take an extra 250 miles with multiple cycles of the vehicle being started and turned off for the light to reset. If light is still on mechanical attention is needed.

This bottle is designed to work in ALL gas tanks including standard, obstructed and capless (no fuel cap) systems. If vehicle has a fuel cap make sure to reinstall tightly, as this can cause the light to be on.

Rislone guarantees, with the proper use of this product, that your vehicle CEL light will turn off if the vehicle has a code listed below, and/or that it will pass that state emissions test. Visit for details of product refund and requirements.

* OBD-II PID CODES P0138 P0139 P0143 P0144 P0145 P0146 P0151 P0152 P0153 P0154 P0157 P0158 P0159 P0160 P0163 P0164 P0165 P0166 P0171 P0173 P0174 P0175 P0420 P0421 P0430 P0431


When the check engine light (CEL) or malfunction indicator light (MIL) illuminates, it has detected an engine system malfunction. Many auto parts stores offer free on board diagnostic (OBD) code checks, and inexpensive readers are available to purchase for do it yourself (DIY) checks. One of the most common codes is P0420 (along with related codes) for the emissions system that usually traces back to catalytic converter efficiency. If the converter is dirty or bad, likely something else caused this. CAT COMPLETE Fuel, Exhaust & Emissions System Cleaner not only helps with what may be causing the light to come on, but also the system that initiated the problem. Driving with CEL on can cause increased vehicle emissions, poor fuel mileage, reduced power, further engine damage beyond what the original problem is, and could eventually lead to vehicle breakdown. Sometimes the damage is so severe that cleaning will not help. For example, a converter that has operated with temperatures over 1300°F will start to melt inside and become permanently damaged. Or an oxygen sensor that is not dirty, but internally damaged. Your best chance of cleaning one of these systems is within the first few months of when the light comes on. However this formula can also work on a vehicle that has had the light on for years. Once the issue has been resolved, the light may continue to be on
for a period of time. For some vehicles, it takes a few start/stop cycles for it to clear, others you may need to disconnect the battery for 15 minutes and leave the door open, then reconnect. See vehicle owners manual for resetting the CEL if applicable.

Many states or regions require regular emissions inspections before renewing vehicle plates or the first time registering. During a visual inspection if there are missing or tampered emissions components, that can be an automatic failure. It also could be something simple like a missing gas cap or a cap with a bad seal. Defective mechanical parts that have failed would be another reason. Many times, it does not take a mechanical issue to cause a failed result on a vehicle emissions test. If you are unsure your vehicle will pass, or maybe it barely passed the last test, we recommend a fresh oil change and emissions system cleaning with Rislone Fuel, Exhaust & Emissions System Cleaner before testing. Other items to consider include spark plugs and fuel filter, if they are due for replacement. This gives your vehicle the best chance of passing.

Available At:

Rislone products are available where auto parts are sold.

Current Deals

$10 Rebate - 4720

Get a $10 rebate with the purchase of our Rislone Cat Complete Fuel, Exhaust & Emission System Cleaner.

Offer is good through December 31st, 2024.

Customer Reviews

Don’t just take our word for it. Our customers have been using our products for decades.
If you have a story to tell, let us know.

“Would highly recommend. 2005 Chrysler Pacifica, 145k and does the Chrysler oil burn. Had a PO420 two weeks before having to have emissions done. With looking at 800 to 1800 bucks to D.I.Y. a cat replacement or mad scientist bench clean it attempt I decided to gamble 40 bucks on Rislone. What’s 1540 compared to 1500 if it didn’t work. Added bottle with 1/4 tank. Ran it empty on highway. Refueled, In less than 10 mi check engine light turned off and had a noticeably drastic increase in power and performance. Passed emissions.

TL;DR, had “cat” code, bought bottle. Followed directions. Worked almost immediately. Passed emissions.”