TLDR Review: Liqui Moly Catalytic Cleaner
Pros
- •Effectively turned off the check engine light in multiple vehicles and kept it off for several months.
- •Improved emissions enough to pass smog tests after only about 35 miles of driving.
- •Provided a cosffective alternative to costly catalytic converter replacement.
- •Demonstrated noticeable performance improvements in different vehicles like a 2012 Jeep Liberty and a 2005 Nissan.
- •Clearly improved catalytic converter function and helped clear P0430 trouble codes after a single application.
- •Reliable and consistent quality from a trusted brand.
- •When applied properly, users reported smoother acceleration and reduced trouble codes.
- •Can be applied through vacuum fittings or near the throttle body for targeted cleaning.
- •Using multiple bottles allows for extended maintenance.
Cons
- •Application is complicated and requires spraying into the air intake downstream of the oxygen sensor—not just pouring into the gas tank, which some find confusing due to packaging.
- •Typically requires two people and specialized spray equipment costing $60+ that isn’t included or clearly mentioned, making it inconvenient for many users.
- •Not suitable for typical car owners without automotive knowledge or proper tools; more intended for race cars or setups with accessible vacuum ports.
- •Application through spray bottle can be messy and difficult to control.
- •May produce a noticeable black exhaust cloud shortly after use, which can be ofutting.
- •Results are not guaranteed for all catalytic converter issues, especially for very higileage or severely damaged converters.
- •Some users found it ineffective for clearing error codes on certain vehicles like a higileage Prius.
- •The product is not eligible for return, so if you’re unprepared or inexperienced, it can feel like money wasted.
Bottom Line
The Liqui Moly 8931 Catalytic-System Cleaner is a solid choice for those who want a cost-effective, brand-trusted catalytic converter cleaning solution that really can reduce trouble codes and improve emissions if applied correctly. However, it’s definitely not a simple “pour and go” fix — it demands specific tools, two-person application, and patience, so it’s best suited for those with some mechanical know-how or professional help. If you want something more user-friendly or a product with simpler application, you might consider exploring alternative catalytic cleaner products that don't require such complicated setups. We think this product shines when you’re ready for a bit of hands-on involvement and want tangible emissions improvements without replacing expensive parts.
Download ShopSavvy App
Compare prices for anything in real-time, set price alerts, watch for deals by keyword, and much more
Install ShopSavvy Browser Extension
Compare and track prices automatically while you shop online at thousands of websites.
Footer 1
Subscribe for Updates
Get the latest news, and updates on ShopSavvy. You'll be glad you did!