well,all this while i am using oil from outside shop so its expensive and i did it at 10k km.Well, the oils sold at Tesco do have the same rating as others and they're the same well known good brands like Mobil & Total. The last oil I bought which is the Mobil 3000 5w40 is also rated as SN oil. Total 5w40 there is also SN, as well as the other brands like Castrol, Shell, & Petronas. I'm doing OCI in my Mark X at 10k km using oils from Tesco/AEON (Mobil, Eneos) for many years already and no problem what so ever. I think you're wasting your money changing it at 5k intervals but it's up to you what ever gives you your peace of mind I suppose.
now,oil is cheaper so can change earlier.
i even used the Tesco brand fs oil in my campro.
not to bad compared to known brand of fs oil.
this is the oil i change at 5k km.
its sold at rm89...half the price of reputable fs oil amd only a tad more expensive than some mineral or semi oil.