What makes a reel loud after you oil it?

What kind of oil did you use? It was probably too thick. Reel bearings do best with very light oils.

Definitely has something to do with viscosity of the oil used unless you have dislodged tiny shivers of metal.

Very tough to say without eyeballing it.

Penetrating oil can wash loose corrosion, putting the dust/mud into the bearings that once clung only to the housings. Sort of like putting cleaner in a fuel tank and breaking the varnish loose actually making more problems..

I'd say something is out of place when you are talking about a noise while reeling. At that point you are talking about a low speed bearing. You wouldn't get a noise on a such a bearing if you soaked it in alcohol and put it right back in there dry. you would feel it before you ever heard it. Most bearings in reels aren't high grade bearings anyway.