Synthetic oils has usually twice or sometimes thrice long change intervals as compared with mineral oils.
ZIC 5000 (Black color bottle) recommends CI as 5K
LM 20/50 Diesel Specialist recommends CI as 5~6K
Toyota TIN Pack CF grade 10/30 recommends CI as 3.5~4K
But when using Fully Synthetic oils for Disels, then SCI should be 10~15K. But there are many things like fuel quality, driving behaviors, engine size, stops & goes, Idling, etc. etc. hence its better to change after 8~10K, but changing both filters after 3~4K is more important.