Stop in for a cup of coffee

Rainy Day Auto said
So I guess rust under the oil cap is normal??

1995 Ford ranger with a 4.0 155k miles

I took the cap off to do an oil change and it's rusty and mushy looking. The rest of the engine compartment looks flawless and clean

The truck runs like an absolute top with no known issues

View attachment 1715436104

No surprise, the moisture from the oil is driven off and it collects under the oil cap and creates a mushy mess of corrosion and other gunk blown off from the hot oil. As long as the rest of the engine is clean, wipe it off and ignore it.