So I've heard some negative things about fuel additives for cleaning the fuel system, and I'd like some conversation on the subject. I've been using Gumout fuel system cleaner about every oil change thinking that it was an altogether innocuous compound. But I've read comments on here how similar products can damage the emissions components. I've recently had to change my 02 sensor, and I'm thinking that might be related to my use of gumout.
Are there any good products will no negative side effects? Is there even reason in the first place to use these?

I've heard that those cleaners can ruin the O2 sensors as well, and I've also always heard that they don't do that much for cleaning anyway.

i don't believe pouring 2-4oz of fluid in with 15 gallons of gas will do anything. that would have to be some pretty hardcore stuff to clean that diluted. plus.. u ever spill gas on anything? paint, grease, etc? gas alone is a pretty damn good solvent.

Fuel additives were a bigger thing back when gasoline was not sold with detergent already added into it. Now, they're a lot less likely to be important. Gum and varnish are largely dealt with by the detergents in gasoline.

Regular additions are unlikely to be of value -- if the gas companies could come up with something to differentiate their gas from something else, they would and do. However, using the fuel system to deliver a compound for a specific job can accomplish something. Seafoam, for instance, will remove carbon deposits that gasoline detergents leave behind. You don't want to run it all the time, because it's unnecessary, but it does what it advertises. It's a more powerful engine cleaner than the detergents you'll find in even Top Tier gasolines, but does much the same job of removing the varnish and gum which traps carbon.

I would however point out that concentration is not really a good indication of whether or not a particular compound is effective. Household vinegar makes a good cleaner compared to water but has only 4% concentration. Though admittedly, for gasoline additives you're typically talking about mixing petroleum products into petroleum products, Seafoam is a 1 oz per gallon gas additive because it's meant to do a bigger job than the preventative cleaning of a gasoline's detergent. For regular use, a low concentration is fine -- but it's already in the gas, so why bother?

Good, informative replies, thank you. So I guess the consensus is it's not really going to help anything huh. Good to know!

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Seafoam maybe in the fuel, but no where else.

For instance people send it into the intake via the brake booster line. Myself included. It did nothing but gum up the carbon, and make me remove the intake to further clean it correctly. Matter of fact, it nearly ruined my throttle body....2 cans of carb cleaner later actually did the trick.

That's surprising, you're the first person I've heard report that Seafoam through the vacuum system gummed anything up. I've used it myself in fact, to real effect. Seafoam actually works as a carb/throttle body cleaner.

Of course, one of those effects was to dissolve the carbon deposit which kept my slow leak on my oil pump seal to a drip, allowing it to become a fast leak, but that's not a negative for the product so much as it was an indicator I really needed to get that seal replaced.

This post has been edited by Galcobar: Aug 9, 2011 - 7:29 PM

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A few more will chime in. Takes a bit for the people that have used it, and actually went and checked on the effects it made, instead of assuming it did something positive. Alot of people read the can, get a positive attitude because it shot white smoke out, and assumed it made a big diff. Far from.

Not hating, just I know for a fact its useless in the intake manifold. Atleast if there is quite a bit of existing deposits.

I shot the whole can up in my manifold and it just gummed it up and made it worse.

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It's actually a pretty common thing for seafoam to cause clogging and also sticking valves. On cars like ours that are non-interference(valves wont meet the piston)/low compression motors there is a lot of room for carbon to build up (also goes for car will LOTS of miles) and sludge build up in oil passages. When you run seafoam or cleaners like it threw the intake it breaks those deposits off the walls but doesn't break them down so they just clog what ever orifice they're in. Thats also a big thing with gas like shell's who add "cleaners" ie try to remove carbon deposits from the motor actually cause blockage.

What about Zmax? Is that just over-hyped lemonade? It's like $20 per application which is 2 or 3 times as much as most of its alternatives. I could see it as just a scam, but I just can't image Shelby lying to me