The 3k-4k mile oil change interval (OCI) recommendation is for the T24A-FTS Turbo. This is because the turbo is cooled with the same engine oil.

If you have a turbo, just accept the 3k-4k mile OCI.

 

Recommended by whom? Do we have statistics that not follow 3000 interval actually cause issues?

 

Nothing “crazy” about changing oil 3K - 4K miles, especially with an oil cooled turbo. Initial oil change was at 1500 for me. Cheap insurance.

 

Sooner on Turbo applications, stock or modified. If you don't then expect early bearing or shaft issues.
If you want to extend it to 5 maybe 6k under normal conditions then use Amsoil Signature, it preformed better in Turbo Coking Tests.
Its what I use in my 1JZ with external oil cooler.