Rubbing alcohol and a tooth brush does wonders for the engine but the muffler is another matter.

Do not use any oven cleaner on your engine. Even the aluminum safe type will oxidize the aluminum. Regular oven cleaner will turn your engine a dull dark grey forever in just a few seconds.

Some people use a crock pot and antifreeze. But do not boil. You will still have to do aa lot of scrubbing. Use a old one and keep it in the shop. Never use it for food anymore.

Sand paper, steel wool, scratch pads, mess up the surface of the muffler. It's then obvious you have been monkeying with the muffler?

Carb cleaner sometimes helps a little on the muffler. I've also used rubbing compound but you have to finish with the white variety.

The best thing is not to worry about the muffler. They'll just get black again.

I'm proud of my black dirty mufflers. It means I have flown the daylights out of the engine.

I like to keep the engine itself clean!

Enjoy,

Jim