Details here: http://diy.stackexchange.com/questions/6226/when-should-i-not-use-wd-40
I know some drivers use WD-40 to de-squeak and lubricate carriage parts, particularly springs. As you'll read in this web site, WD-40 is not really a permanent lubricant. It's too thin for that purpose plus it *attracts* dirt.
Kroil) and as a temporary lubricant to get you and your equipment to the time and place where you can use a more permanent, more appropriate lubricant.
So far, for me, I find good quality spray silicone lasts fair long and does NOT attract dirt or even leave any visible trace (i.e. good for use on high quality polished carriage parts.) I mainly use it to quiet carriage leaf springs.
Usually this fix last forever....well, I can't actually swear to that since I haven't lived that long.