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Overheard a guy at the scrap yard talking about quenching in used motor oil

I was picking up some old leaf springs in Toledo last weekend and this older guy was telling his buddy he only quenches certain tools in 10W-30 he drained from his truck. He said it cools a touch slower than new oil, which he swears helps with stress on thicker pieces. I'd never really thought about the age of the quenchant mattering before. Has anyone else experimented with different used oils like that?
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3 Comments
oliverk80
oliverk801mo ago
Huh, I've actually had good luck with old transmission fluid myself!
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sean_torres71
That old guy in Toledo is onto something. Used oil has more crap in it, which actually makes it a bit thicker and cools slower. I've found that works better for avoiding cracks in thicker, high carbon steel, like those leaf springs. Just make sure you strain it first, unless you want a bunch of burnt clutch material stuck to your work.
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wendy391
wendy3911mo ago
Sean_torres71 is right, but man, that strained oil still stinks up the whole shop.
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