Mystery oil spot on cab floor

[Snowman9000]

This is on my Chevy Express 4500 van Class C cab.

I had oil residue in the seam between the rubber floor and the entry molding, on the driver side. Photo below. In the photo I had already wiped it clean. The high point was at the left of the highlighted area, and it stopped at a low point under the seat where the seat attachment bolt is.

It had spread up on the rubber floor about a half inch, the way that oil typically will spread. It might have been there quite a while and I never noticed. There were a few dead bugs and other debris.

It was not water. It was oil. Well, it could be brake fluid, but it felt like oil. And it's not a diesel engine, either.

So I have a mystery. I don't carry oil or fluids there. The engine compartment is pristine. I took photos around the drivers side if anyone needs proof. 🙂 I mean, it is squeaky clean. Same thing under the dash. It only has 15K miles. Maybe some oil change tech did it, I suppose.

Can you think of any mechanical reason for it to get there?

[j-d]

On our Ford, that whole step well "bucket" pulls out easily. If you can pull yours, it'd let you lift the carpet/matting and give you a look under. Factory might've left an oily rag under there. I worked for an Olds dealership in the early '60's. Auto workers sometimes left "gifts" in odd places. I remember flashlight batteries in a door, and a Coke bottle with a note inside "Bet this drove you crazy."

[Bessie-Hunter]

My truck did the same thing. It has power seats and the dealer could not find anything leaking from the seats. (Both of mine have leaked)

[azrving]

Could well be brake fluid. Look up at the pedal linkage and rubber boot. There is also refrigerant oil in the ac system but probably very unlikely and would probably take a catastrophic ac leak to blow oil out. Check the brake reservoir too.

It's been so long since I've worked on that stuff. So they are using a hyd pump/steering type pump for brake boost?