Up to now the axis show no values for minor grids. In case of logarithmic
scaling this is not good. 
In the old chart the minor grid has ticks at:
For 2 intervals at 5
For 3 intervals at 3 1/3 and at 6 2/3
For 4 intervals at 2.5 and 5 and 7.5
That has been the same way as for example MuPad does it.

In the new chart the minor grid has ticks at:
For 2 intervals at 5.5
For 3 intervals at 4 and 7
For 4 intervals at 3.25 and 5.5 and 7.75
The new chart has a different grid than the old one.

I tried to find out whether there exists a standard for setting minor grids. It
seems that there is no standard, but the charts with logarithmic minor grid
which I found, write values to the minor grid, so that the user knows, where the
grid is.

Excel works around the problem by not such minor grids but always uses minor
grids with 9 intervals. Those have ticks at 2, 3, 4, 5, 6, 7, 8, 9 in both methods.

In OOo the user do not know where the grid is and it changes from old to new
chart, therefore I suggest to write values not only for the major grid but for
the minor grid too.