How is the van running? Do you have a check engine light? How many miles? It COULD be a lifter noise (I’m not sure what engine is in the vehicle), which would be irritating, but not extremely damaging. If it is an overhead cam engine, the valves could need adjusting. If the shop you took it to said it was not a problem, and didn’t try and sell you anything, why are you concerned? Just trying gather evidence to help you.
I remember reading about a Caravan (I forget what year exactly) that had what sounded like a lifter noise. The guy who was working on it checked everything in the top end of the engine and everything checked out just fine. It turned out to be the number 2 connecting rod was knocking, which was making it sound like a lifter tick.
Like beefy said 10w30 should not be that big of an issue unless it really really cold out.
You need a mechanics stethoscope (or a screw driver) and listen around the engine to try and pin point where the sound is coming from.