First time user of this product. 16 year old Chevy truck with 206,000 miles 5.3 V8. I've used Seafoam fuel treatment regularly over those 16 years but never anything focused on catalytic converter cleaning. The truck wasn't throwing any check engine lights nor was it experiencing any noticeable sluggishness prior to using this product so I can't necessarily say I've noticed any increased performance since. Fuel economy seems to be exactly the same and the engine sounds the same as it always does. I purchased this off the recommendation of a friend with a high mileage truck that claimed to experience a big increase in engine performance as he was having sluggish and poor running issues along with a noticeable increase in his fuel economy, saying it was more like the MPG he had when it was new vs the decreased mileage he'd had for a while. Anyway, I won't say this didn't do anything productive, I'm sure it cleaned something down the line. I will, in my opinion, say this stuff is quite overpriced. Now, had I been experiencing issues and other products failed to remedy and this product was successful, the price would be considered reasonable and on par with similar fuel additive offerings. For me, I'll stick the the seven or eight dollar can of Seafoam once or twice over an oil change period. My regular use of that appears to have me running just fine for a lot less.