Brother MFC-J6510DW Software User's Manual page 29

Printing
Advanced Duplex Settings
Some types of print media may need more drying time when using the duplex feature. Change
Advanced Duplex Settings if you have problems with smudged duplex prints or paper jams.
Normal

Choose Normal to print at normal speed, using a normal amount of ink.
 Duplex 1 (Slower print speed)
Choose Duplex 1 to print at a slower speed, using a normal amount of ink.
 Duplex 2 (Slower print speed & less ink)
Choose Duplex 2 to print the same speed as using Duplex 1, but using less ink.
Note
Duplex 1 (Slower print speed) is not available for Ledger or A3 size paper.
1
1
22