LS1 teardown underway, and it's not looking pretty

Bank 1 Pistons

Bank 2 Pistons

Cylinder Heads

I know I can use carb cleaner, but was intrigued by a suggestion online to use automatic transmission fluid (ATF), especially since I have a leftover bottle of the stuff.

I fully intend to try it out and update this with an answer, but meanwhile would be interested to know if anyone else has ever tried this option.

  • Much of that carbon will stubbornly resist carb cleaner.
    – Carguy
    Mar 6, 2017 at 8:06
  • @Carguy definitely. I've tried carb cleaner, throttle body cleaner, brake cleaner and engine degreaser. Nothing seems to cut it.
    – Zaid
    Mar 6, 2017 at 8:13
  • See my answer, below. Marvel Mystery Oil is mostly a hydraulic oil that softens the carbon over the course of days, allowing the carb cleaner to become highly effective. You will be amazed!
    – Carguy
    Mar 6, 2017 at 8:21
  • I've very effectively cleaned many heads through the spark plug hole using this combination of MMO & carb cleaner, usually in about 10 minutes on a warm engine. I've also cleaned impossibly difficult outdoor grills in the same way.
    – Carguy
    Mar 6, 2017 at 8:26
  • You could try to use a 1:1 mix of ATF and acetone (for the love of everything holy to you: please do that outdoors)
    – Martin
    Mar 11, 2017 at 10:04

3 Answers 3


Yes, ATF is highly effective at cleaning carbon, but Marvel Mystery Oil is even better (it's ATF mixed with dry cleaning fluid). If cold, allow the fluid to sit for at least two days, then spray with carb cleaner. The longer, the better -- many guys have freed frozen piston rings without disassembly by letting the fluid sit for weeks.

The warmer you make the parts, the faster it cleans. I've personally cleaned heavy deposits from piston crowns on a warm engine in a mere 10 minutes. Old, salty marine mechanics will warm an engine that is not running with heater coils or by pumping hot water through the block.


Used it a lot back in the early 70's, seemed to be common knowledge in all the Dealerships and was Very effective at removing carbon deposits on the pistons and cyl. Head areas.


Much more efficient and effective (and you are sure the waste is disposed of) to take it to a machine shop with a high temperature chemical cleaning machine.

  • How does this answer the question about ATF fluid? Mar 5, 2017 at 15:36
  • This might answer my need, but doesn't answer the question. For starters, I don't know of any such machine shop in my locality, and I'm sure there are many others who have encountered or will encounter a similar situation
    – Zaid
    Mar 5, 2017 at 15:41
  • If you read the instructions on the container does it say it is suitable for cleaning? If not, then don't use it....... Replies to @Paulster and OP
    – Solar Mike
    Mar 5, 2017 at 16:25
  • up voted this because it contributed.
    – user22295
    May 27, 2019 at 19:54
  • I upvoted because it is the most effective method, in my opinion. Machine shops are not that hard to find.The result is so far superior than dabbing at it with a dirty rag and solvent it's not even close.
    – Tim Nevins
    Dec 26, 2019 at 21:52

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