I use/favor Valvoline Full Synthetic Grease. I did an informal test about 15 years ago, placing dab of about six brands (Phil Wood, Valvoline Synthetic, moly based, Lithium based, etc...) and types of grease onto a piece of cardboard and setting it in the sun in the summer when there was an extended number of days when the temperature exceeded 100F consecutive days. After a month of exposure to light and heat, the only grease that did not change colors or start to break down was the Valvoline Synthetic.

The test was prompted after I bought a tube of premium priced Phil Wood grease (like $10 for a small tube). After servicing the bike's bearings, I put the bike on my roof rack, on a day when the temperature was over 90 degrees. The Phil Wood Grease ran out of all of the bearings and made a mess of the bike and the car's roof, before I even had a chance to ride the bike.

Phil Wood was the grease with the rep when I spent the money on it. Little did I know that the melting point was so low. After the incident with Phil Wood running out of the wheel hubs and bottom bracket, I threw the tube in my tool rollaway, and while the tube was mostly full, in the summer that year, it melted and leaked out of the tube, making a big mess in my rollaway.