This machine operates at one speed ... it is not like it has a transmission and you can shift from drive into over drive. There are a few things you can do, however.
You can remove the print driver and reinstall with a fresh copy ... go to www.oki.com/support
to get the latest driver available for this printer, which works with your current operating system.
There are features in the driver which will let you make the machine appear faster ... print in draft mode for example ... Your printer may be in HI quality mode and you may select a lesser quality print for another. Since I am not intimately familiar with this particular printer, I can only suggest you go into the printer profile and examine the options you may find acceptable.
To locate the profile, open the control panel, open printer folder, find and open your printer and take a look around.
Thank you for your quesiton this morning @ FixYa.com