I am pretty new to baitcasters. I have two Lew's Pro G's which I bought brand new about two months ago. The fish like a dream. However, I followed the instruction in the box for maintenance, and added a drop of the oil supplied with the reel, onto both ends of the shaft, and in the other oil port near the bottom of the reel. Anyhow, Since then, one of the reels whistles really loud when I cast now. The reel casts just as well as it did out of the box, but it makes that noise, and it's driving me nuts. Any ideas? Anything to worry about? 

at the lube port on the bottom of the reel is for grease to be applied to the gear , not oil . take off the brake side cover and put a drop of oil smeared on a q-tip and run it around the inside of the race of the spool ( where the centrifugal breaks touch) in the picture - on the right ( brass ring )

That was easy. Thanks! No more whistling!