This is what I use.

For a heavily soiled interior

Plastics & rubber
Meguiar's D103 All Purpose Cleaner Plus at 10:1
Follow up with Meguiar's Quik interior Detailer to utilize the light cleaning ability to remove any residue left over by APC+
Follow up with Meguiar's Ultimate protectant (used every 2 months)
Buff to knock the shine down and remove any excess product

Leather
Meguiar's D103 at 10:1
Leather sealer system (used every 3 months)

Lightly soiled interior
Plastics & rubber
Meguiar's Quik interior Detailer to utilize the light cleaning ability to remove any residue left over by APC+
Meguiar's Ultimate protectant (used every 2 months)
Buff to knock the shine down and remove any excess product


Leather
Meguiar's Leather Sealer System (used every 3 months)