My engine runs very loud (lifter noise) until it gets really warmed up - then it quiets down. Someone suggested that I use Gunk Motor Flush in my oil to remove sludge deposits. Does this stuff really work? Can I do more damage? Also, do I need to drain some oil out before adding the Gunk so I don't go over the fill line?

The Gunk directions say to add the product with engine cold, run for five minutes until warm, then change the oil and filter. It says not to drive with the gunk in.

Any suggestions are welcome.