You should do what the BIR's do
Blend the garlic and ginger with the oil
You can also add a little water and salt, but that's not necessary
Keep it in a sealed container in the fridge
I use mine a month after I made it, with no ill effects
And it won't turn bluey green
I use a full bulb of garlic ,a similar volume of ginger, 2 tablespoons of veg oil, 2 tablespoons water and half a teaspoon of salt
If I'm making a larger quantity, then I don't bother with the salt and water