hi, i was just curious to know, i put some 5w40 into my car, it is the recommended for it, but, i am not sure if the owners before put in the same or put in the cheaper 10w40, what would it do having about a ltr of the 5w4 out of 6.5 of other, would it do any harm, or?
BMW are 'keen' that 5w40 is used .. although on higher mileages (ie over 100K miles, one would use a 10w40)
You certainly will not do any harm topping up with some 10w40, but if you are below 100K miles, I would stick to 5w40 and get it from GSF Parts or the like.