I had the same issue after warming up to running temp. I tried different oil and additives with no luck!
Then took it to my tech and he put 10w-40 "diesel oil" with the STP lifter additive and no sound now. But it's just a bandaid...
Im sure I will just replace my lifter when I have time.
[CENTER]2009 [COLOR="SlateGray"]SILVER[/COLOR] JK Sahara
RC 3.5-315.70.17 on Stock RUBI's
PE Front and Rear Bumper
DIY DECK LID
2006 Navy WK HEMI ~RK 3.5 lift - 17" Moabs - Toyo 265.70.17 AT - Bedliner Paint Job - [COLOR="Red"][B]SOLD[/B][/COLOR]
'85 XJ... Still tryin to figure out what the heck I have in this piece of Junk! But you gotta start somewhere