Just a quick tip for usage of waste oil :
When you change your oil and have 5-8 litres of waste oil, mix the oil with wood preserve (Creosote) and spray on your fencing panels. I have done this for the past 5 years, and panels still look like new.
Another tip....
If you are struggling to fill your gearbox or diff with oil.....try using a pump action fence paint sprayer. I have 2 paint sprayers, 1 for the oil filling purpose and 1 for the fence panels. They are about £20 each. If you try filling oil in diff a conventional way, I seem to bang my knuckles and end up like I've been 2 rounds with Frank Bruno.
Cheers
Tony