Realistically it all depends on your climate. I know with Castrol edge, they say you can go for 10000km (6 months) between oil changes.....maybe in California where the temp is more stable all year around and not 9 months of winter where I'm from.. I feel oil is oil but synthetic is better than conventional. Stick with whatever is recommended in your manual or by dealership. In my case it is the castrol edge.