Novel How much dialouge is too much dialouge?

Anytime the dialouge is not leading to the next thing that will contribute to the story, I think it should be left out. Example.

A:I'm leaving mom, I'm going to the store.
B:Okay Bob, be careful
C:Where's Bob?
B:He went to the store.
C:Say...have you seen my glasses?
B:There on the counter.
C:Thanks, so how is Martha?

versus

A:I'm leaving mom, going to the store.
B:Okay Bob, be careful
C:Where is Bob?
B:You just missed him, he went to the store.
C: Darn it, I needed some milk. Let me see if I can catch him.

In the first example Bob going to the store does little to help proceed the story, in the second example Bob goes to the store and character C needs something for the store as well. Thus Bob's statement for going to the store in the first place is somewhat justified isn't just a statement that otherwise could've been left out to the readers.

 

Don't forget there's character as well as story. Dialogue can be used to establish character as well as progress narrative.