Here is some semi-valuable advice for y'all!
Believe it or not, there really is a solution for the sludge problem. Costs more as it may, nonetheless I use 10W 30 synthetic oil in all of my cars and advise all car concerned customers to do so. Never use semi synthetic or even high grade conventional.
The first time that I changed my oil to synthetic, you cannot imagine how fast the oil went dark from conventional organic oil sludge and had to be changed. I thought that I was losing my mind and asked several family members if I hadn't just changed the oil?! This turned me into a true Mobil 1 believer.
Do not believe the nay sayers who will tell you it is of no advantage or that you cannot change once you have used conventional. The problem with these motors is that these engines are made offshore and basically suck. Remember the cheaper part for them means that the more profit is to be made.
And also if you use a product like an engine flush, most likely you will end up with a gasket leak-a-rama. While I have not seen the engines, some of the problems that I have read here seem to be other than a manufacturer defect.
My friend who owns this intrepid was not savvy to this problem. She purchased the car from someone who evidently was and thus got rid of it to her. However before I was involved the engine has blown last fall and failed while driving as the timing chain broke.
At any rate you cannot properly "rebuild" these engines as the tolerences are so "thin", and if you try a low mileage used one from a junkyard, basically you are only going to recreate the problem once the car hits over 60k again. Accordingly the car really is not worth to put a new motor in as the value for resale is low.
I feel very badly for all the hard working people on here who are in these prediciments still owing money on them, and will have no choice but to make the expensive repairs.
No matter how often you change your oil, conventional is always a losing bet especially in these engines.