I would be careful about using a cleaner, then using synthetic. Both may make oil leaks happen.
Personally, depending on how bad the sludge is, use a higher quality oil. Good oils already have detergents in them to combat sludge. Using cleaners could mess up the chemistry in the oil, thus making it less effective.
I use Castrol GTX 5w-30 with a Bosch oil filter, and after 3,000 miles, my oil is still fairly amber.
If you are using a Fram oil filter, stop, they are junk. The filtering quality of those filters in laughable. The bosch is more expensive (about 2x the cost) but the quality of my oil after 3000 miles with the Bosch is so much better than the quality of my oil after 3000 miles with the Fram.
Just curious, but how do you know that you are getting a lot of sludge?
From what I've heard, Seafoam should only be used in your oil for 10-15 minutes. Using a warm engine, put in the seafoam before an oil change, idle for 10-15 minutes, then drain and refill with new oil. If may not be a bad idea to use an extra quart to rinse that shit out before you refill.
1995 Altima GXE (sold)
2002 Subaru Impreza WRX
2001 Yamaha YZF600R
Last edited by bkal; 02-18-2007 at 04:54 AM.