Check out the following tests
Testconnections2 returned 0.23 seconds, Testconnections3 returned 4.68 seconds, that's a factor of 20 slower. If there is any pooling done here, it's either not working for me, or it's kind of not very effective.
What am I missing?

    Public Sub testConnections2()
        Dim cmd As New OleDbCommand
        Dim da As New OleDbDataAdapter(cmd)
        Dim conn As New OleDbConnection
        Dim dt As New DataTable
        conn.ConnectionString = My.Settings.b040_beConnectionString
        conn.Open()
        cmd.Connection = conn
        Dim n As Long
        Dim t As Date = Now
        For i As Integer = 1 To 100
            cmd.CommandText = "select Art_id from Artikel where Art_nr = '  125'"
            n = cmd.ExecuteScalar()
            cmd.CommandText = "select * from artikel where Art_Nr = '  125'"
            da.Fill(dt)
        Next
        Debug.Print((Now() - t).ToString)
    End Sub
    Public Sub testConnections3()
        Dim cmd As New OleDbCommand
        Dim da As New OleDbDataAdapter(cmd)
        Dim conn As New OleDbConnection
        Dim dt As New DataTable
        conn.ConnectionString = My.Settings.b040_beConnectionString
        cmd.Connection = conn
        Dim n As Long
        Dim t As Date = Now
        For i As Integer = 1 To 100
            conn.Open()
            cmd.CommandText = "select Art_id from Artikel where Art_nr = '  125'"
            n = cmd.ExecuteScalar()
            cmd.CommandText = "select * from artikel where Art_Nr = '  125'"
            da.Fill(dt)
            conn.Close()
        Next
        Debug.Print((Now() - t).ToString)
    End Sub