Which ink does the Brother MFC-J815DW use?

The Brother MFC-J815DW (inkjet, 2019) uses LC3033BK, LC3033C, LC3033M, LC3033Y.

Compatible cartridges

CartridgeColorYieldPagesOEM priceCost/page
LC3033BK black XL3000 $35.00 1.2¢ OEM · AmazonCompatible
LC3033C cyan XL1500 $20.00 1.3¢ OEM · AmazonCompatible
LC3033M magenta XL1500 $20.00 1.3¢ OEM · AmazonCompatible
LC3033Y yellow XL1500 $20.00 1.3¢ OEM · AmazonCompatible

XL/high-yield cartridges usually cost more upfront but lower the cost-per-page — better if you print often.