if you can remove that fan often there is a sticker on the motor hub, remove the sticker and you should see the bearing. sometimes under a rubber plug, sometimes not. add a drop of light oil (like sewing machine oil or 3-in-1 oil) to it. that can add a few months but likely youll have to redo it every month or two.
Sintetic engine oil will do a much better thing. I use Castrol engine oil and lasts much longer.
interesting. you use the lightest weight oil you can get? at least very light oil was what was recommended back in the day, like 20-30 years ago when i was using and rebuilding very small fans on electronics and early computers. and engine oil then was typically 30 weight or more. thick oil would sometimes prevent the fan from starting and sometimes they would not attain the correct rpm as these were pretty small low power fans back then though.. now engine oil is much lighter and fan bearing are probably much different in lubrication requirements, or at least the bearing themselves are larger.
Doesn't seem to matter, I've been using motor oil for a couple decades or close and it all works well.
Keep in mind that this is a short-term solution in any case, since the seal(s) is(are) shot and the oil isn't going to stay there for long.
I'm not sure how straight 30 weight would work, I normally use 5w-30 10w-40 or 5w-40 in my vehicles so that's what I have around.
I did the bearing re-oiling for many of my old Radeon GPUs and especially any Gigabyte Windforce GPUs.
Most GPU fans of mine never had a sticker that could be peeled and behind it was the bearing. Most I had to drill a hole thru and later seal up.
With the crappy Gigabyte Windforce, those I just used some floss and yanked out the fan blade and put a drop or 2 of mineral oil.
Mineral oil worked best because it was slightly thicker than oil such as 3-in-1 which is too thin and slightly thinner than motor oil which is too thick.
The 3-in-1 was too thin and basically the oil seeped out way too quickly and you had to re-do the job in a couple weeks. The motor oil was hit or miss but on some GPUs, especially if near a cold window, the oil would cause the fan blade to stick and you had to manually flick it to get it to spin.