A process for reducing haze in a heavy base oil includes: obtaining a first effluent oil by contacting a hydrocarbon feedstock with a first catalyst including a zeolite of the ZSM-12 family; and obtaining a second effluent oil by contacting the first effluent oil with a second catalyst including a zeolite of the ZSM-48 family. A hydroisomerization catalyst system having reduced haze includes: a first catalytic region having a first catalyst disposed therein, the first catalyst including a zeolite of the ZSM-12 family; and a second catalytic region having a second catalyst disposed therein, the second catalyst including a zeolite of the ZSM-48 family. The first catalytic region is disposed upstream of the second catalytic region.