What would be the best lubricant for lock mechanism on uPVC doors please? The window company that supplied the doors suggest WD-40 or silicone spray but I read somewhere that use of WD-40 is not recommended & graphite powder is preferable.
use Graphite grease (its a powder). Use WD-40 or Vasaline they will work but they attract dirt and you will then get more problems with stiff or sticking locks!