I have a different opinion and don't recommend lubricating PSU fans. For one, anything that plugs into the wall can kill! And while all PSUs are supposed to bleed off any residue (and deadly!) voltages within a few seconds, you cannot assume those bleed-off circuits are working properly - especially if the PSU is not behaving properly in the first place. While admittedly, being killed is not likely, receiving a nasty zap is certainly possible - and not fun, especially in a high-wattage PSU. So digging around inside AC to DC power supplies is something I only recommend for folks familiar with electronics safely, preferably certified electronics technicians.
Also, many of the better fans today use permanently lubricated bearings with special grease. Applying the wrong lubricant (like 3-in-1 oil, sewing machine oils, or the wrong grease) can actually break down the bearings' lubricant and increase friction and wear and tear.
Finally, as Masterchiefxx17 noted your PSU is still under warranty. Opening the PSU case WILL
void the warranty! Considering those 750W G2 supplies have a whopping 10-year warranty, that would not be a good idea!
Do note that the EVGA G2 series of PSUs is typically considered a top-tier product. They have received outstanding reviews at many of the better review sites. I personally have used several EVGA Supernova 550W and 650W G2 supplies in recent builds and love them. I have a 550W G2 in this computer right now and I am very happy with it. And the only fan noise I hear is from my furnace down in the basement! First day of Spring and I woke up to 27°F and a dusting of snow outside!
Sadly, it would seem you might have got a lemon.
Until Man can create perfection 100% of the time, even the best will have some samples that fail prematurely.
But you really need to determine what the noise really is. Is it a grinding noise suggesting something is bad with the bearings? Or is the fan just spinning at full speed and making a lot of "normal" fan noise?
If grinding, then definitely get a RMA for warranty support. Depending on where you bought it, since it's been only a couple months, you may be able to return it through them. Otherwise, EVGA's warranty support is supposed to be pretty good. I am sure they will honor the warranty. Sadly, unless you bought it locally, you will probably have to pay shipping one-way.
If the fan is spinning full speed, make sure your case is providing an adequate supply of cool air for the PSU.
BTW, each of the G2 supplies I got came with a little PSU tester connector to connect to the 24-Pin PSU connector. This devices tricks the PSU into thinking it is connected to a motherboard to let you power up the PSU outside the case. Assuming your 750W PSU came with one of these too, I suggest you plug it in and see what happens. The fan might spin up to full speed initially, but it should immediately settle down to near silence, or even off.