No, you should absolutely not use WD40 to clean your CPU fan. WD40 is not designed for use on electronics, and it can damage your hardware components easily. We also do not recommend using ANY type of lubricant on your CPU fan, as this will attract more dust and debris, which will clog it up faster and even potentially ruin it.  If you want to lubricate the fan bearings, we suggest using a silicone-based lubricant, as this won’t attract dust. However, you will need to be comfortable removing your CPU fan from the case and opening up the fan to reveal the fan bearings. Only do this if you know how to install and uninstall hardware components.