2005 4.7L Ticking, Milky-white @ oil fill
 

2005 Durango SLT, 4.7L, 159,000 miles

Engine has had a light "tick" for over 4 yrs, developed while I was deployed overseas. Wife had it looked at by more than a few shops/dealers. Got many different answers (manifold gasket, valve/lifter issues, etc...). One independent mech changed the oil a couple of times and the tick quieted down considerably, and stayed that way for the last 4 yrs/30K miles (oil changes every 3k-5k miles). Last week I changed the oil (5W30 high mileage as always) and about 2 days later the tick gets louder than ever- quieter as it warmed up, but still significant. Checked oil dipstick and level was about 1/2 qt low. Opened oil fill and there's milky-white residue on oil fill cap and all inside the oil fill reservoir. Dipstick isn't milky, and as far as I can tell there's no oil in the coolant system. Is this a head gasket issue, or something else? Thank you in advance for any suggestions you can provide.