Engine sludge

How can I tell if my car a 1999 chevy cavalier has engine sludge?

drain the oil and check for sludge in the oil. auto parts stores like autozone sell a engine flush fluid that you put in the engine via your oil cap and run the car for five minutes DO NOT DRIVE VEHICLE WITH THE STUFF IN YOUR MOTOR after the five minute turn off your car and drain the oil. replace the oil filter, do not forget to put the oil drain plug back in and put the recommended amount of oil back in your car. if you don't want to do this I know for a fact goodyear tire and rubber company AKA goodyear automotive will do it for you for around $30 which is a fair price.

Sometimes you can see some sludge on the dipstick but generally you need some disassembly to detect it.

Engine flushes can do more harm than good. Sometimes loosening sludge allows it to migrate from someplace where it does no harm to someplace where it will block oil from doing its job.

Your best bet is to change the oil and use good oil. Synthetic oils produce the least sludge but on older engines can increase oil consumption. Occasionally changing from mineral to synthetic oil will cause problems but I've never seen this happen. Also avoid short trips. Sludge is produced when oil is mixed with other things like water or coolant. Short trips do not heat your oil long enough to boil off the water. Try combining short trips so you can run your engine longer.