Bought a car that is supposed to have been rebuilt sent receipts for rebuild but dipstick has sludge on it. So is there something I can put in the engine and run it to clean it up. I am not at a point to tear it down.
Probably better off not disturbing it. Just do an initial oil change and maybe another one in a few hundred miles. Change the oil when it's good and hot. Might not have been run long enough to dry it out(who knows).
Maybe pull a valve cover and check oil drain back holes to make sure they aren't clogged.
years ago our station serviced several trucks from the local grain coop. now if you are a country person you know how they treat their vehicles. anyway they all get full of sludge from lack of maintenance and abuse so what we would do to clean the engine out is drain all oil. pull valve covers and clean them out, change oil filter and put 6qts of kerosene in the engine and start it up. let it run for at most a minute then shut it down and let it sit for a day or 2. drain out the kerosene and change filter and re-pete the process. only this time after it runs for a minute then service it with fresh oil and filter with an additive in the oil.. when you drain the kerosene the first time you wont believe the crap that will come out.. after you service it and put some miles on it change the filter.. then go a thousand miles and change filter again. after that, service as usual..
now i will add if you have a potential internal problem such as bad lifter, cracked or bad rings, bad oil pump etc this process will bring it to light real fast. but if the internals are sound you wont have any problems...
I personally have not done it but have known people that have substituted one quart of automatic transmission fluid instead of a quart of motor oil when they changed the oil and supposedly that helped to cut loose some of the sludge.
You didn't say what kind of car it is. If the valve covers are to hard to take off look down in the oil fill hole / tube. If you just want "Fix-it-In-a-Can". Change the oil and pour a can of SeaFoam in it and drive it 1000 miles. Change the oil again and your good to go.
Now take a good look at the oil, SeaFoam mix you drained out.