Yes yes yes!!
The fumes even when spraying on Steel or Iron are nasty...mind the Wind or Breeze!
Anyone who has used 'Oven Cleaner' in their Oven, would know the experience...
Breeze can carry fine over-Spray on to your Arms or Face...so, be mindful...have a Gallon of Apple Cider ( or any other ) Vinegar handy in case you need to neutralize the Lye.
I have been very pleased with Oven Cleaner for cleaning off old Engine Sides and Bell Housings and Rear end Axel Housings and so on, while they are in place.
The old Cars and Trucks which had Oil seepage and Oil Fumes, mixing with Road Dust, can end up really being seriously dirty with old, baked on grime.
Solvents generally do not work very well to remove it.
Olive Oil can work quite well, if one has time...soak it in let it sit a day, scrub off with strong Soap and Water and a Scrub Brush.
Crystal or Granular Drain Cleaning Products, are really good for letting parts Soak iin a Bucket or 55 Gallon Drum.
I used to have a steel Drum with the Band-Held Lid, which I used to clean Parts with Caustic Soda in Water.
Old Backing Plates, Linkages, whatever, just scrape off the worst first with a Putty Knife, then lower into the Drum with an Iron Wire, and let stew a few days.
And again, Kids, Dogs, Birds, uninformed visitors...you really need to practice good cautions with these things.
Keep a secure Lid on any Cuastic Soda 'Tanks', whether they are 5 Gallon Buckets, or a 30 or 55 Gallon Drum...and or keep unauthorized personel or pets well away from the stuff.
The 'Hot Tanks' used by engine rebuilding places, were simply Caustic Soda which is kept warm or Hot.
A Steel Deum of the same Solution, left in the Summer Sun, can get pretty warm for free, or, it is easy if one wants to have a Burner under it.
I found it works just fine at ambient temps, with no need of being heated...so I never bothered heating mine.
Anyway, 'Oven Cleaner' is Lye...as are most of the Powder/Granular/Crystal "Drain Cleaners".
These are for cleaning Iron and Steel only.
Probably be okay for Brass or Copper also.
But not for plastics or Aluminum or Magnesium Alloys or Pot Metals, as Jon relays, you can get poisonous fumes, as well as that it will 'eat' the Pot Metal or Aluminum/Magnesium Alloys.
Olive Oil can ruin some plastics, but would be fine for Aluminum/Magnesium Alloys...soak it in well, let it sit, scrub with an appropriate Brush with strong Soap and Water.
