Using Fuel System Cleaners: Where Does the Debris and Gunk Go?

I recently added a container of Red Line cleaner to a fresh tank of gas. I did so, not because I was having any obvious driveability issues, but because I purchased the car used and it had a questionable (i.e., non-existent) maintenance record. Figured it couldn't hurt, and I've been satisfied with previous Red Line products and usage.

Here's the question, and it relates, I suppose, to all fuel system cleaners, especially those that claim to get rid of carbon and other deposits. Where does the dirt and debris that's cleaned go? Is it picked up by the oil, perhaps filtered, burned in the combustion chamber, swept away by exhaust gases, or, perhaps, magically dissolved into nothingness? Any thoughts on what happens to the junk?


I tend to put Techron in my last tank before an oil change in case it liberates anything into the oil …
Probably no big deal either way unless you run the oil too long
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Site Donor 2021
Carson City
They are solvents that dissolve impurities that are burned away in the combustion process.
Just like the stuff we use to detox our liver.
And just like 4WD said. I put it in last tank before OCI, drive it down to about 1/4 tank which is about 450 miles and change the oil.
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This is a good question for Trav. Just like everyone else has mentioned, the “gunk” should get lifted in suspension and burned out the tailpipe in the normal combustion processes.

Now if you’re talking about particles that can’t be dissolve, one would have to ask themselves how undissolved particles got there in the first place. Theoretically, your fuel injector filter baskets can trap indissoluble contaminates but to me that’s not the fault of fuel system cleaner.
There are a few types of deposits, one is varnish and the other are hard particles that found their way into the fuel system either from the station tank or the fuel tank in the car which is usually rust particles in metal tanks, white corrosion from aluminum fuel rails that have run an incompatible fuel, corrosion in the injector itself (especially older types that were never designed for alcohol laced fuels) and rubber particles from deteriorating hoses.

Varnish will dissolve and go right through the injector and burned in the combustion process, rust from tank will get trapped by the pickup screen and main filter. In theory the injector filter should capture anything larger than the actual nozzle size but in reality the small particles congeal and can cause blockage.

The fuel system cleaner releases them and lets them pass through or at least some of them, other times the filter will get so dirty with particles too large to pass through that it hinders flow removing them and cleaning the injector is the only way to get it clean.
If the engine has DI it may have a different issue that nothing but replacement can fix and even then if it has gone too far the particles can get trapped and will not come out.

This is very common on some VW/Audi, Mazda and Fords. these have burned out and the nylon particles have gone into the injector nozzle.
I did manage to get these back to 100% but nothing in a can or through the line cleaning is going to help this.