Trying to upgrade weapons....cannot find oil.

Have you found?

Yeah, there's different sizes of oil cans scattered about. I've found them around gas stations and industrial sites.

Edit: Also there are some wandering vendors that sell it in bulk. I just can't afford it yet.

Thanks!

Paint cans! Also another oil source.

Also, and can't recall exactly what it supplies, collect fire extinguishers. I always forget them as in previous fallouts you could not take them.

lighters and lanterns have oil too.

You can make Cutting Fluid at a Chemistry station. This junk item breaks down into 3 Oil and something like 1 Steel.