Listen to what sir @Xulfiqar is saying.
I acted upon his advise (darte darte) and i am now stretching fully synthetic 5w30 caltex oil till 10k on oem filter. Now this time planning to extend the oci to 12k as the car runs mostly on highway. The per km rate has dropped a lot for me keeping in view the rising lubricants prices.
One got 2 options
Use guard filter with cheapo mineral oil and change on 5k kms if it is run on highway mostly. If it is running in city mostly then change on 3k km
2nd option is use good fully synthetic oil with oem filter (i buy filter from 3s) and change on 10 to 12k if the car runs on highway mostly. If it is used in city only then change on 8 to 10k km
I am following the 1st option for my vitz which is reducing oil though engine power etc is good and for my corolla which is used on highway mostly, i use the 2nd option.
Keep in touch with sir Xulfiqar to bust the myths of our local mechanics and dealerships.