seat Alhambra 1.9 diesel - 20,000 mls servicing intervals - Silver Senior

What effect on engine life will service intervals of 20,000 mls have as opposed to regular 10,000 mls servicing. ?

seat Alhambra 1.9 diesel - 20,000 mls servicing intervals - unthrottled
Impossible to predict. But frequent oil and filter changes is the cheapest, easiest insurance you can get.