With that many miles, I'd just keep doing regular oil changes, until the engine needs to be replaced. With that many miles and as much gung as their is, the only way your going to fix it is to rebuild it, but you might as well get as many miles from it, as possible.
Accutally a small wire brush and a vacuum cleaner as you brush it off would probably work the best then take a sample of the gunk and try different solvent/engine flushes to see which will work the best on any left in the engine before you dump the flush in so you will know if it completely dissolves it before you use it.
Thanks for the input everyone.
I don't use this car much at the moment (only weekend drives and such), it does something like 2500 Km a year. It's hard for me to understand this condition since I serviced it as per the owner's manual since new.
Maybe I should just drive it as is, for fear of making things worse?
I will research more on Auto-Rx and high mileage oils though, thanks for the links!
edit: Read a lot of positive reports on Auto-Rx but it would take me more than two years to do the required 2500 miles clean and 3000 miles rinse cycles!
...It's hard for me to understand this condition since I serviced it as per the owner's manual since new...
Vehicles that aren't driven actually have a worse life than vehicles that get used all the time. After you drive it and park it, it will cool off and then the hot air inside the engine turns into condensation which the forms a surface layer of rust. If the engine doesn't get used for a long period of time then the oil that was clinging to the inside walls of the engine starts to migrate to the bottom leaving the metal completely unprotected to humidity. The longer it sits the more rust is formed. Then the piston rings get stuck in one position inside the pistons. When you attempt to drive it again, all the piston rings are stuck and allowing the combustion process to blow right past them. This turns the oil black almost immediately. Next problem is all the rust being mixed into the black oil and then pumped throughout the engines oil ports etc. It all churns up and mixes into a black gooey mess.
Parking a car is really abusive, and if the car is parked for a long time (ie: over a month) you should start it and let it warm up, then immediately change the oil. NOONE ever does this, including myself- but in a perfect world...
ITS THE OIL MAN ! ! ! IT MAKES THE SLUDGE ! ! ! YOU ALL HAVE BEEN FOOLED into thinking that it is the way you are driving the car that forms the sludge but it all comes from the oil!!....
Don't get so excited man, calm down. LOL We're just having a friendly discussion, nothing too serious. I have my own experiences, and my own examples over the last 19 years of rebuilding engines, racing cars, etc. Everyone else has their own opinions and experiences also.
Your also right- the sludge comes from oil, but it's also caused by a combination of driving habits and cheap oil. Sludge is formed from oil that is burned/overworked/full of carbon etc. A quality oil will not lose it's viscosity as quickly when exposed to those conditions. However, some oils have less detergents and fail to remove carbon and soot from cylinder walls, so they stay cleaner "looking" and appear to last longer while the engine is filling itself with crud.
So in a case where the engine is not used much, you can't get away with cheap oil.