I noticed this the other day when I was installing a new radiator. It looks like oil seeping from the joint where the manifold bolts to the head & just wondered if it's anything serious? The truck hasn't been driven in about 2 and a half years - only started it every few weeks to keep the batteries charged & I'm just trying to get it road ready again. Any help or advice much appreciated - thanks!

 

Leak looks small enough that I personally wouldn't worry about it at all.