What kind of oil should I use?

I have an old fan that looks like it came off of some factory
machinery.

I've had it for 30 years, but I think it's 50 to 90 years old. ??
It still looks original. (though the blade used to slip a lot, and
took 60 seconds to catch up to the speed of the shaft, until I glued
the two pieces together)

It used to be it only required oiling once a summer, iirc, but that
has gradually gotten more frequent. Even though just 5 years ago, it
lasted for 2 months once, even then it was usually every 2 weeks, and
now it is every day or two.

What oil should I be using? It has no oil ports, unless you call the
hole in the case right next to the shaft a port. At the other end,
with the blade, I have to tip the motor face up and use a long spout
oil bottle to place oil right where the shaft comes out of the
bearing.

When it needs oil, over the course of an hour or two, it gradually
slows to a stop, and the motor itself gets hot, and because I"ve been
sleeping, I think I've let it stay stopped and hot for hours. But
when oiled again, it seems to run just fine. I suppose it's too old
to have oil-impregnated bearings. (When did those come out?)

I've used 3-in-1 oil, SAE 20, 10W-30**, and I'm wondering if I should
use thicker or thinner. Should I use gear lube (SAE 90 iirc) or try
to find something in the middle like SAE 60***. Is sewing machine oil
thinner than SAE 20 and 3-in-1? At any rate, I have some thin oil in
a clear plastic tube, with a 2mm tube for applying it.

I know I could try every one of these but I need some encouragement.


**Yes I know the additives aren't needed, but at first it seemed to
work better than other oils.

***I could buy a quart of 10W-50 for the car and use some of that.

Please don't tell me to throw the fan away. The only alternative to
better oil is oiling it every day. Last year I got a bigger fan
with 3 speeds that does a wonderful job keeping me cool all night, but
I still want this one, which is the only one small enough to fit on my
window sill, right next to my bed and my head, and which I can turn on
or off just by lifting my arm to the switch on the cord. . I could
nail a shefl to the sill and use a bigger fan, but I'd rather oil it
every night before I go to bed. I keep looking for a simlar fan,
including ebay, but no luck. And if I did buy one, I'd still have to
fix this one.


Thanks.

Unrelated to my qusetion, I think, It's all metal, all black enamel
except the blade and the wire grill around it. It has a thin,flat base
4 or 5 inches square, with holes at each corner, which I think held
screws or rivets that held it to the machinery, or maybe a tractor or
fork-lift if they had fans so long ago. From the base is a mini I
beam going up to hold a motor a little bigger than 2 decks of cards,
on on top of the other. The shaft is closer to one end of the
rectangle. The wire screen is barely any protection from sticking my
fingers in the path of hte blade. It has one blade, or two if you
count both ends. It certainly doesn't oscillate.