Ticking like a Time Bomb (Engine Noise)

[SMITH23H2SUT]

At engine start-up after sitting for 12 hours my 2005 HUMMER with 62k miles on it makes a ticking sound( Sounds like it's low on oil ). During my last oil change at Jiffy Lube they inspected it for leaks and found no signs of a leak. It appears that the sound is coming from the engine compartment and not underneath the truck. After it warms up awhile the sound goes away in about 10 min., I tried Lucas Oil treatment and that seems to work until my information on oil reads 65%. Should I switch to a heavier oil? Could it be something other than the oil? Oil pump?