All other answers are 100% incorrect. Why? Because the question you pose is not complete. Sludge is he remains of oil gone bad due to being used for too long or when the engine oil is cooked by one or a series of engine overheats. Just like anything on this site, words are used to describe items, most of the time, incorrectly by children with cars and no money. You not reveal the car's brand, model, engine information, miles, mechanical status and, most importantly, the level of sludge. Now, the level of sludge can only be determined by an expert. You are not one. Only mechanics are. Only mechanics have the training, experience and equipment to determine what proves, system, materials to be used when removing sludge from a motor. The add anything to an engine that can cause the sludge, a solid, into the oil system will cause the blockage of the oil ports that drip oil to bearings and valves and other moving parts of the engine causing the engine to fail. Since you do not know about cars and due to the potentially seriousness of the situation, only a mechanic can render proper servicing of this engine. That is the only responsible way to answer . I suggest you use Google Search to locate information next time. Getting opinions from invisible strangers as to mechanical conditions of cars is not advisable. We offer advise and counsel, not repair nor service lessons. OK?

If you do it yourself you will have to use a engine flush additive and run the engine and flush several times to get rid of the sludge. Becareful because some engine flush additives can be caustic and damage parts. If the car is very old it can cause leaks to the water pump. Some car shops use a reverse method to back flush and engine.

If your motor is that sludged up and you use a flush product all the sludge will break loose and end up in the oil pan. Then it gets sucked into the oil pump and plugs the screen. Now you end up with a blown motor due to no oil pressure and the connecting rod bearings and crankshaft bearings seize. I'd highly recommend not flushing your motor if it still runs!

Ideally, regular oil changes. This is one of the MAIN reasons for regular oil changes.

Fact is, if your engine is full of sludge, it probably has advanced wear on the piston rings, and is about due for an overhaul.

I recommend running it until it dies, which probably wont be very long, then replace the engine. Flushing wont remove all the sludge, and what's left will probably clog up the works and do more damage than good.

Believe it or not, if you start using Mobil1 Extended Performance Motor OIL and change it every 5,000 miles. Sooner or later the sludge will be gone.

not a good idea stirring the sleeping junk, but drain oil, add 5 qts kerosene, start when warm, do not revv, let run until warm or 15 minutes max. never load the crank! best to just clean it out without chemicals or kerosene

When I need to flush I just push the chrome handle.................

SERIUOSLY.... ADD MARVEL MYSTERY OIL TO ENGINE OIL AND DRIVE IT A WHILE THEN DO AN OIL CHANGE.

MANY SHOPS ACTUALLY HAVE A SYSTEM FOR FLUSHING, IT'S EXPENSIVE BUT SAFE AND WORKS GREAT.

Next oil change use full synthetic oil.

Edit: if the current oil level is low then add a quart of synthetic oil then next week change the oil with full synthetic oil.

never put kerosene in a motor Harry you dumba$$

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