Hi,
I will use L gear when i am climbing slope on D.
When there not enought power.
Or coming down a long slope, as i don want to over heat my brake.
Use L gear as engine brake.
To change to L from D, please make sure your Latio is at very slow speed 20 to 30 KM/h.
As changing to L from D, from high speed will actually spoilt your transmission.
Hope it help