I agree with kidvermicious on pretty much everything except not recommending seafoam. You just aren't going to find a proper scientific study on the effectiveness of seafoam that wasn't done by someone making money on the conclusion, so all you will get is anecdotal evidence on either side. For my part, a couple guys I trust, and who didn't make any money off my buying into it have given me some compelling tales of seafoam making a big difference in recovering an engine. It isn't a magic bullet, and won't take you from sludge to pristine, or from seized to perfect (though one story from a moto restorer friend was of an engine so packed that he was going to scrap it rather than waste the time cleaning it, and the seafoam got it cleaned well enough to run and be restorable without a ton of work), but anything in there that will help to breakdown the sludge will help. Seafoam has been around forever, so I feel it's pretty safe and well understood. You can also put some ATF in there shortly before changing as it also has more detergents than engine oil.
I usually put some seafoam in a couple hundred miles before the oil change, and then like kid said, change the oil while HOT. If you are going to do that, be super careful not to burn yourself getting the plug out. I use a pneumatic ratchet to just spin it off without getting my hand where near it.
I think the seafoam/atf will help break up what sludge is there, and changing the oil hot will help to flush it all out. And kid is right, better to use the cheap stuff that you can afford to change every 2k or so rather than break the bank on syn and change it every 3-4k. IMO syn is for being lazy (which I am) and changing every 6-10k, or whatever the bottle says. I do alot of highway miles on my commute, and 6-10k is much nicer than every 3k, which is every 2 months or so.
