Try slightly different grades of oil, the hydraulic lifters use the engine oil to work, this may help, I would try slightly thicker oil when warm, the first number is the cold viscosity and the second number on the oil container is the warm viscosity, i.e 5w40 is thinner than 5w50 when warm but they are the same when cold or on start up, the bigger the number the thicker the oil, slight ticking should not cause damage either just a bit annoying, the oil is deffo worth a go, make sure it is still good quality and fully synthetic and only slightly thicker that what you have in, say 5w 50 instead of 5w40, let me know how you get on ok
