It's interesting you say that... Synthetic oils don't necessarily last longer than mineral oils. The oil itself isn't the problem - its the detergents, friction

It's interesting you say that... Synthetic oils don't necessarily last longer than mineral oils. The oil itself isn't the problem - its the detergents, friction modifiers and things that break down through heat cycles and over time. As a rule with my vehicles, they get new semi-synth every 7,000kms. When I had my last car (Direct injection petrol turbo), I changed it every 5,000. And that oil was cooked each time. Having pulled the tops off more engines than I could count, you can immediately tell an engine that gets regular oil flushes compared to one thats run on longer intervals. Sure, the engine might last your whole ownership without having a serious issue... But inside it'll probably tell a different story.