I've been a longtime fan of Scotty's channel. My wife is the original owner of a 2006 Nissan Xterra which now has about 145k mi and has been almost perfectly maintained with one exception. About 5 years ago, I watched Scotty's video on how to clean a catalytic converter using lacquer thinner. I used this for Bank 2 a couple of times before saving up and replacing the cat in 2019. A few years later bank 1 code came up. Again, I used the lacquer thinner method a couple of times, and here's what happened next. 

I was on a road trip in July 2022, when I had a complete breakdown on the highway with the engine overheating. I had the car towed to the nearest Nissan dealership where they replaced an engine coil, the destroyed cat, and a few other things that totaled $2,260. After that, my engine began sucking oil at a rate of about 5 qts every 1,000 mi. From what I can best surmise after bringing it to several mechanics, the cat pieces got sucked up into the engine and wreaked havoc. There were all kinds of metal shavings in my oil after that. I did a compression test which came back ok but still burning a ton of oil from presumably ring and valve wear. That all happened at around 141k mi. 

I barely drove the car after that as I saved up $8k to replace the engine with a remanufactured engine which I replaced this month, over a year and a half later at around 144k. 

The new engine seems to be running great, but once I reached about 50 mi on the trip odometer it just threw me another bank 1 cat code. This sucks because now I guess I've gunked up the cats again running it with the bad engine for those 4k miles. 

This whole mess including all of the diagnostics at several shops testing the failing engine is going to end up costing me over $12k more than had I just replaced the cats from the very beginning when the p0420 lights came on without trying to "clean" them. Not to mention a ton of hassle and frustration trying to figure all of this out over the last 1.5 years and having limited use of my vehicle during that time. 

If you love your vehicle and want to properly maintain it, my recommendation is to not attempt to clean your catalytic converters or you may suffer an unexpected $12k loss like I did.  Please share your thoughts. I wonder what percentage of cats completely crumble like mine did? Do you think the risk/reward ratio is worth trying to prolong the life of your cats with cleaning? If 100 people get away with cleaning per 1 complete engine ruin maybe it's worth it to try for some but if you are one of the unlucky ones like me that is costly. Was I just a victim of probability and unlucky in this case? 

I would love to hear Scott's thoughts and the thoughts of the community. Had I known that this was even a possibility I would have sprung for the new cats from the beginning.