Link to Scotty Kilmer's Video: http://www.youtube.com/watch?v=5icTmYItwiE After watching Scotty's video I was curious if it would actually work. Since we know from my video on diagnosing catalytic converters that the catalytic converters in my Subaru were bad, I though it was a perfect opportunity to try out this theory. I used about 1 quart of lacquer thinner to about 7 gallons of gas. I drove a total of 200 miles and tested the converters. The testing showed a very slight improvement but nothing that I would call significant. It was worth a try. I can say that I did not notice any issues with drivability during or after the test. It may not have fixed the problem, but it didn't seem to cause any other problems either. I feel the check engine light that came on was just a coincidence and not the result of putting lacquer thinner in the gas tank. Here's some useful links for you. Diagnosing a P0420: http://www.youtube.com/watch?v=9VZ5K8n5jj0 Discussion about this video: http://www.ericthecarguy.com/kunena/18-The-EricTheCarGuy-Video-Forum/47854-does-lacquer-thinner-clean-catalytic-converters#77372 The best place for answers to your automotive questions: http://www.ericthecarguy.com Facebook: https://www.facebook.com/EricTheCarGuy?fref=ts Twitter: https://twitter.com/EricTheCarGuy Google+: https://plus.google.com/100195180196698058780/posts Information on Premium Membership: https://www.ericthecarguy.com/premium-content-streaming-etcg-content Stay Dirty ETCG Due to factors beyond the control of EricTheCarGuy, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. EricTheCarGuy assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. EricTheCarGuy recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of EricTheCarGuy, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not EricTheCarGuy.