Hi,
It's the vehicle manufacturer that specifies the oil change interval.
8,000 or 10,000km is good, I say 8,000kms because I am in the UK and actually measure it as 5,000 miles (much easier to read the odometer at 5,000, 10,000, 15,000, 20,000 miles etc). personally I would not leave it until 15,000kms.
As a rule of thumb the oil should be changed every 6 months or 8,000/10,000 kms whichever comes first.
Over the years I have watched oil change intervals increase ( even for the same basic engine and oil type.).
Miraculously the same engine and oil can now last longer !!!!
Think about it ? By offering longer service intervals the vehicle becomes more attractive to a potential customer, lower running costs etc.
It started with Japanese vehicles. The rest of the world played catch up.
You have to realise that most people will think 200,000kms is a reasonable working life for an engine. With a little care most engines can easily run for 300,000km plus.
Car manufactures are giving service intervals that are just enough for the car to reach 200,000 miles without premature failure during the warranty period.
Oil is the life blood of the engine. Save a few rupees if you want. I prefer the peace of mind and proven results I have seen over the last 50 years.
I work as a vehicle mechanic in a garage and every week see an engine that has self destructed due to oil failure. Especially as a result of diesel contamination cause by DPF regeneration cycles, often resulting in wet cam belt failure and turbo failure from an oil feed blocked by wet belt debris.
As mentioned in my first comment these intervals are " normal usage". Some intervals can be as low as 5,000kms depending on operating conditions and oil type, google Ford Transit oil change intervals.
Keep in mind the cost of oil and a filter versus a new engine.
Drive safe, Neil
