cleaning/dissolving oil

[Murderface]

So tonight I went to coat a pair of valve covers off a friend's car. We scrubbed the covers with some mineral spirits and sanded them down like usual. Then when we put them in the oven to preheat...it burned so much oil off that it smelled like somebody was running an engine in the house that had all the seals blown out of it.

Apparently, we didn't get enough of the oil residue off for it to not burn like mad. What do you guys do to completely dissolve oil off of parts that have it heavily caked on? These covers had some PCV ducts that we couldn't get inside to clean so I was thinking of letting them sit in something for a long time to dissolve the oil.

A friend of mine suggested soaking in gasoline for cleaning oil off stuff (not for powdercoating, but in general) but somehow gasoline+oven does not seem like a good combination to me. What do you guys suggest?

[Harleydad]

Simple Green

[Murderface]

Let it soak in that? or just give it a good scrub with it?

[Harleydad]

Get the concentrate and mix it 50/50. Soak the part and hit it with a pressure washer. If you don't have one, visit your neighborhood car wash.
I've had some good luck with something called "Krud Kutter". It's found at Menards, Fleet Farm and the like. Usually in the paint section where have the strippers, acetone etc........