Will a car battery slowly discharge if the positive is left diconnected and the negetive treminal is connected to a ground rod.No circuit would be made back to the source so no current would flow is my first intuition but then the how do you expain capasitive circuits.Since earth ground is 0 reference would there not be a potential for electron flow?

The short answer is no. You just have to be sure there is no discharge path. The capacitive effect is nil on a DC circuit. It only affects a changing voltage. Any DC current you see across a capacitor is actually a fault.

Greg,
Thanks for you response.I hate to be a pain but could you elaborate on what you mean by "You just have to be sure there is no discharge path"DC theory has never been my strong suit and I want to fully understand this question as pointless as it is.Believe it or not two electrical engineers came up with a definitive "I don't know" after mulling it over.Sorry for my atrocious spelling as I was in a hurry typing my last post.

In theory it would not. However batteries are a chemical reaction that is ongoing. A battery will slowly lose its charge just from internal losses.
You can also lose charge if the battery is dirty on top. There can be discharge across the top of the battery through the dirt.

Mr Devlin has summed it up well, If the top of the battery is dirty, it can create a fault path that will slowly discharge a battery, even if one terminal is disconnected.

Batteries do self discharge. Even very stable batteries like lithium have a shelf life and eventually will die on the shelf.

So if you want the battery to be any good many months from now, a float charge is in order. It doesn't take much current after the battery is topped off. That is with a battery cable removed.
Joe