Can I reduce running time for Full System Manual Scan?

Sometimes I run the Full System scan manually.  It takes about 1h 45m to run.  Is there anything I can do to get it to run in less time?  I always close my other apps beforehand, but it still takes about the same amount of time to run.  The “number of threads for manual scan” is set to auto.  Would it make any difference if I set it to 8 or 16 instead?