Originally Posted by
krazygl00
Do not use WD40 on your shifters. "WD" stands for "Water Displacement" which is what it is really good at. Spray WD40 down seat tubes after rainy rides, and use it to clean out Chris King hubs, but never spray it into any moving parts you want lubed. When it evaporates it leaves a gummy residue of mostly mineral oil which is not very good at lubricating metal parts but is super good at catching dust.
There have been many many posts on this forum and others about how well WD40 has cured numerous troublesome STI shifters. WD40 saved my 9-speed D-A shifters from being replaced many years ago and they are still working perfectly. WD40 helps loosen hardened factory grease and remove dirt and other crud from the shifters. Many bike shops use this same cure.
I suggest you search through the forum archives.