Weird. When I was a youngin’ the exact same thing happened to me except back then it was a 1972 Dodge Coronet Custom, and you know what Custom stood for. That usually mneant that the car was a completely stripped down version of what it was without all the extras-. Extras! Like a damned radio! Dad, you may recall those times.
Anyways, what we were told to do by our awesome mechanic–you don’t see them anymore. This guy was an elderly grizzled fellow with a cigarette hanging from his lip and an old half lame German Shepherd laying on the store’s front porch that was one of the sweetest “junk yard dogs” I’ve ever known. You had to step over him to get into the place, but he didn’t mind a bit as long as you patted his head when you passed.Once you got into the repair area, it was a hurricane toos of tools and parts, new and used, thrown everywhere, all of them covered with grease. But Jack knew where every single item was, at all times. His son worked under him and couldn’t screw on a tire bolt straight but Jack was possibly the best mechanic I have ever known. He was also one of those rare breeds who didn’t mind helping out a down-on-their-luck person. When the car threw a rod–that’s how we found out about the "sludge"in the engine–he knew we were a young couple just strating out with very little of our own and charged us a whopping $7 labor to replace that rod. Even back then that was dirt cheap. I always wondered how he came up with the number seven for a price…
Anyways, what he told us to do is to change the oil, without fail, every 1,000 or less miles for the next five or six changes. He made sure to press the "don’t skip and wait until 2 or 3 thousand every now and then. If we did as we were told, it should clean it out, and the car should run alright afterwards.
Well,Jack was right.We traded that Dodge Custom in four years later and it still ran well. By then we both had full time work and a new house and were well on our way. I like to think that a lot of that had to do with what Jack did for us (And the did that several times over those early years.) The only reason we got rid of it is because little things began to go, and those little things start to add up, it’s time to buy a new (or newer) car. So we got almost what we paid for it and bought a brand new 1979 Diplomat, two-door, six cylinder, with a landau vinyl roof, A/C, an AM/FM stereo radio with two front and one rear speaker! We got it at a steal cuz that was the year Chrysler was going bankrupt and Lee Iococca came to the rescue.
They also make a whole lot of additives that are allegedly designed to clean out your motor, but I’m still not fully sold, though I am getting closer to it. I’d do a bit of research on a few of the better ones and see what folks who have actually used them have to say. Sometimes they do some good even when you least expect it, or WHERE you least expect it at some other part of the engine or drive train.
So ideally, you should have them flush the system, but that would be a more expensive option. And I’d use the ‘high-mileage’ oil, with a low viscosity rating, maybe 5W-30, for at least a few of those oil changes. I know the car doesn’t has high mileage, but the oil probably was never changed. That’s where all that sludge probably came from. If it was changed or changed near its regular schedule, the build-up wouldn’t even be seen, not at 40 thousand miles. So the particulate matter flowing in and around all the parts inside that engine and the cylinders for all that time, never being changed and just getting worse and worse, has most likely done more harm than most 40 K mileage engines would see. But yeah, of the two, the flush out would be best but the do-it-yourself option sure as hell worked for me. I hope it works for your sweet daughter. Sounds like you’re a Dad who sincerely cares. That’s a great thing for a daughter. Take it from one who’d been there and knows. Good luck to you and her!