What minerals would I want to keep in my cooling system?

>From: Rob <becida@COMCAST.NET>
>Reply-To: Rob <becida@COMCAST.NET>
>To: vanagon@GERRY.VANAGON.COM
>Subject: Re: distilled water for coolant - was New Car Dealers And Parts
>           Prices-a service advisors
>Date: Thu, 31 Jan 2008 05:12:17 -0800
>
>This "sucks the minerals out of your car" is the argument that comes
>up every time. Prove it.
>Distilled water is just water...
>
>Rob
>becida@comcast.net
>
>
>At  1/31/2008 03:27 AM, Mike wrote:
>>  Distilled water has no minerals in it.  Because it's 'wants' to have
>>minerals in it, it 'takes' minerals from where ever it can get them;
>>that'd
>>be the inside of your cooling system.  This is a form of corrosion and
>>eats
>>away at any thing that it can get it's greedy little claws into.  I
>>believe
>>that it has been proven to accelerate the breakdown of your engine's case
>>and heads, gaskets, radiator, heater cores, etc.
>>  Anyone else familiar with this issue?
>>
>>Mike B.
>>
>>----- Original Message -----
>>From: "Rob" <becida@COMCAST.NET>
>>To: <vanagon@GERRY.VANAGON.COM>
>>Sent: Wednesday, January 30, 2008 11:12 PM
>>Subject: Re: distilled water for coolant - was New Car Dealers And Parts
>>Prices-a service advisors
>>
>>
>>>At  1/30/2008 05:28 PM, Allan Streib wrote:
>>>>On Jan 30, 2008, at 7:39 PM, Vdub Guy wrote:
>>>>
>>>>>I plan to flush my coolant system soon and replace it with VW blue
>>>>>coolant and distilled water.
>>>>
>>>>why distilled?  Is that what VW calls for?  Or is your local water
>>>>really extremely hard?
>>>>
>>>>Allan
>>>
>>>Distilled water is a known, tap water, who knows? I always use
>>>distilled when mixing up coolant.
>>>
>>>
>>>
>>>Rob
>>>becida@comcast.net