My Mini One 07 seem to be burning atleast 1 litre of per month, I am unsure whether it is due to daily motorway travel of 90 miles return trip. I been shelling out £40 for 5 litres of Castrol edge 5w30 (Autosave Components - View Product -> Castrol EDGE 5w-30
). Is there a cheaper alternative brand (shell, Havoline, asda or tesco) similar to Castrol which can do the same job? I have heard rumours you can mix different brand of motor oil as long as they are the same specification. Please can someone provide confirmation?