The minimum amount you can order is 500 litres (excluding Northern Ireland). Domestic tanks typically range in size from 1,000 litres to 2,700 litres. If you do not have a gauge to tell you how much oil you have used, some tanks have a sight tube on the outside so you can see how full your tank is.
If you have neither, then a garden cane or similar can be dipped in the tank to act as a dip-stick to give an indication of the oil level.
