Will Fuel System cleaner ruin the oil that's in the engine?

[NewRacer]

I've heard that the Fuel System cleaner (the one that put in the fuel tank) will ruin the oil that's in the engine. Is there any proof?

[v-cam]

I don't see how, unless you have a really bad intake leak directly into your engine oil to which case your car would be stuffed anyway.

I have used it before without a worry.

[marc780]

Maybe you heard that this happens when a shop does an injector clean. This is where they hook up directly to the injector fuel line and force pressurized solvent through the injectors. When this is done, the cleaner is undiluted by gas. And on top of that, the professional grade cleaner is much stronger than the kind from walamart that we dump in our tank.
The professional grade solvent chemicals are so strong that they can damage the bearings, etc. So yeah, if this is done, they often do recommend an oil change right after because theres a good chance some will make its way into the oil.
But for the regular gum-out type stuff, nope, never seen it ruin an engine.

[Hajoca]

It is 'leak down' or cylinder 'blow by' where the piston rings don't seal well, then what you get is the fuel diluting into the crank case. If concentrated solvent is used, then it will end up in the crank case and ruin the oil.

[NewRacer]

Originally Posted by Hajoca

It is 'leak down' or cylinder 'blow by' where the piston rings don't seal well, then what you get is the fuel diluting into the crank case. If concentrated solvent is used, then it will end up in the crank case and ruin the oil.

But that doesn't happen to healthy engine, correct?

[toyomoho]

If you are just putting fuel injector cleaner in the tank, you will not have a problem. Follow the directions. If you are worried, put the cleaner in the tank 3-400 miles before you change the oil.