Favorite daughter mechanical story- she called me at the office, in a panic- "I just put some motor oil in the power steering pump- is it going to wreck it?" No, I told her, a little oil won't hurt anything- power steering fluid is just oil anyhow, but a little thinner, with additives- we'll have a tutorial when we're both home.
So she pops the hood, and showed me where she put the motor oil- and it was the oil fill! Somehow the caps had gotten switched, so it said PS. So I switched the caps back, end of problem. Analytically, its a little like the old saying "I thought I made a mistake once, but I was wrong."