Oil change intervals are not as simple as people make it to be, the worst offender which destroys engine oil is cold running an engine constantly.
Otoh, you cannot expect an oil with API CB or CC to work in a DI type diesel like the 1KD.
The correct lube type and reasonable working environment like urban driving in pk can easily allow a normal service interval of 10,000-15000 kms with inspection in between.
Harsh environment warranting a 2500 kms change would be a quarry or mining truck that lives underground all its life or desert runner (choki vehicle)
And im really surprised why buyers simply refuse to buy such a shitty truck which requires 2500 kms oil change of 8 litres with urban driving. Thats the poster child of how not to make an engine and also adds insane level ownership cost of such a utilitarian vehicle like a hilux.
I know I would literally walk out after seeing it requires a 2500km service interval of a full 2 gallons of engine oil and new filter. As thats about question 4 or 5 to the sales guy from me.
For long change interval in Pk, ask the radio cab fleets (if they exist yet) - in the past they would run their xli corollas to 15000 kms on the same cheapo 10w30 oil with topups in between, some vehicles engines would not shut off for 4 days straight too. (3 shift vehicle, literally hired mule type usage)