So... as the title says. I accidentally added fuel cleaner to my transmission, which is currently leaking (meant to add stop leak as a temp fix if it worked).

I grabbed the wrong bottle and didn’t catch myself and now I poured cleaner into my system.

I couldn’t find anything online about what damages, if any, this will cause or if I can just ride it out and be fine. Or change transmission fluid immediately.

Thanks for any information!

  • If you had used stop-leak as you intended it would have been just as bad or even worse for your transmission. That stuff will not only clog up the leak, but also contaminate the transmission. Might even cause the transmission to seize up if the car isn't used for several hours. How I know: A cousin of mine tried that on his motorcycle transmission which had a minor gasket leak. He ended up needing to replace the whole transmission on his Honda Goldwing.
    – Tonny
    Commented Nov 1, 2018 at 9:34

1 Answer 1


You should drain this immediately.

The solvents may very well damage the seals etc in the transmission - you don’t make it clear if it is an auto or not.

So, drain, then refill and run for a bit then drain and refill again.

If you have not run it yet, that is even better...

  • I'm of two minds as to whether to recommend bringing the car up to operating temperature before changing the transmission fluid. I think I would at the end of the day, otherwise the fluid won't drain well, but don't run it any longer.
    – GdD
    Commented Nov 1, 2018 at 8:44
  • @GdD personally, I would drain it straight out and refill and go from there - in the hope that the cleaner only gets to be in the oil pan and not circulated past all the seals etc
    – Solar Mike
    Commented Nov 1, 2018 at 11:36
  • That's a good point @SolarMike.
    – GdD
    Commented Nov 1, 2018 at 11:38
  • I'd pull the pan and change the filter as well. Agreed to not let this stuff circulate. If an auto, getting this stuff into the torque converter makes for a whole new level of ARGH! Not because I think it would hurt the TC, but rather because the TC holds so much fluid, you're going to be hard pressed to get it out of there without pulling and completely draining. Commented Nov 1, 2018 at 12:00
  • @SolarMike sorry for the delay in response. The cleaner should be auto. I am not 100% sure because I don't have the bottle. It is honestly too late for me since I had run it for the past two days before I noticed that I put the wrong thing in by mistake. I am making plans to drain my fluids in the near future, but I have a question to ask. I only put about .141 liters in... Which I think is about 2% of my total fluid and I already lost probably about a quart of fluid already due to the leak. What do you think is the chance that it is such a low concentration I don't have to worry about.
    – Matthew
    Commented Nov 2, 2018 at 7:49

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