On my last several rides I've noticed a noise that has become progressively more pronounced. It sounds like a "ping" sound from the wheels. My first thought was that it was coming from the front wheel, however when I put my bike in the stand after a ride to check things out I noticed an excessively loose spoke on the rear wheel. I tightened this up and hoped that would solve the problem. No dice, over the next two rides the sound continued. I checked again for any noticeably loose spokes and didn't really find any.
After reading the relevant section in my Bicycling Magazine's guide to bicycle maintenance, I found a description of a sound that seemed similar to mine that originates from where two spokes crossover. I went back to the bike and started squeezing spokes near where they cross and sure enough I was able to reproduce the sound I was hearing.
Now to my questions (sorry for the long lead-up). The book says you can just oil those crossovers and wipe off the excess. My questions are:
1) What type of oil should I use for this? The only things I have in my tool box right now are chain lube, citrus degreaser, grease and WD-40.
2) Is this more of an annoyance that can be alleviated with some oil, or could it be a symptom of a larger problem? The bike is pretty new with only around 300 miles on it (I had my warranty tune-up not long ago). Also I noticed the rear wheel is a little wobbly and is probably out of true - but it's not rubbing the brake pads and since I'm still a newbie to all this, I'm somewhat reluctant to start trying to true the wheel myself.