Verified answer

sludge is a known issue with these engines. Here's why.. the engine tolerances are tighter and the engine oil gets hotter and stays hotter than it should.

Not a problem.. the solution: synthetic oil.

First what I would do is buy a quart of Marvel Mystery Oil and do an oil change, subbing 1 quart of motor oil with the marvel. the MMO will do a slow and safe cleaning of the engine, and will break up the sludge. So you want to drive with the MMO in for about 3000 miles. So use a conventional oil.

after this oil change, switch to a synthetic oil. Yes it will cost a few dollars more initially, however, synthetic oil has several advantages conventionals don't. synthetic oil does not sludge. It handles excessive heat and excessive cold. It offers slightly better mileage (which I've never seen), but the main thing.. it lasts longer. So an avg. conventional lasts 5000 miles with regular driving. Synthetic can go minimum 12,000 miles. No joke.

I would recomment using 0w-40 Mobil 1 (European formula). And a quality oil filter, no fram. Get a wix or purolator.

change ONLY the filter at 6000 miles and top off with oil. You'll save money in the long run and the oil will last 3x as long.

toyota engines of late 90's early 00's have a sludge problem too. the tolerances are so tight the oil boils and starts to sludge. toyota blamed the consumer. (of course). the solution is synthetic oil.