I am posting this in luv-main as as far as I am concerend this is an issue
of critcal importance.
I have found over the years fans (usually sleeve bearing) will eventauall
get noisy. For some time like most people I simply purchased new fans, I
have found though that most sleeve bearing fans can be lubricated greatly
extending there life. I am posting this at this time as I have found over
the years they usually become noisy around this time of year. I in fact
have just done a couple yesterday.

The procedure is to get access to the fan, place it horizontally with the
actaul fan down. Under the label in the centre is a depression around 7 to
8 mm dia, this has the fans thrust bearing in it. A couple of drops of
machine oil, making sure one does not get any oil out side the bearing is
all that is required. To reseal for most fans I use a square of insulation
tape. I have a number of 80mm fans still going well after 10 years using
this procedure.
Now if one has some Thermaltake fans one job is good deal easier is these
have a rubber plug over the bearing (under the label). In this case one
carefully removes the plug with a sharp implement making sure not to
damage it, a couple of drops of machine oil and replace the plug.

It may take some hours for the fans to become completely silent again, the
longest time so far has been around 5 or 6 hours.

I have been doing this now for at least 8 or 9 years with only a single
failure, even then I did not give the fan enough time for the oil to
penitrate.

IMPORTANT Note, Do __NOT__, I repeat do __NOT__ use motor oil, this oil
WILL gum and eventuall sieze the fan. I use sewing machine oil avaible
from most supermarkets.