drain interval are dictated by the manufacturer of the engine, follow that and dont try to mix up recommendations.
e.g. heavy diesels of container pullers having 80,000 kms oil change interval usually have twin oil filters and about 40 litres oil sump capacity,
Do not try to run your CD70 on one oil change for 80,000 kms
similarly dont try to run your container puller on 1500 km oil change intervals