There are three main types of engine flush. One is the 250+ml can like Justice Brothers type of engine flush which you pour into the engine oil filler and run/drive for about 15 min to half an hour. Contains strong detergents to remove sludge.Other type is the lighter oil like those sold by Shell and these also contain detergents. Basically a 4 litre pack. You drain the old oil/ leaving the filter on and let the engine run for 10-15 minutes at low RPM as recommended by Shell. You then drain the lighter oil and change to a new filter.The third type involves using cheaper mineral oils instead of the engine flush (the second method).Pros and Cons.Been told that the detergents can be harmful to the engine - , i.e. damage your gaskets, seals etc, dunno how true that is. If you believe its true, then the last method is for you.I prefer the second method, but would suggest that it be done once every four services or so.Done the first and second methods - not at every service tho. Even done the first and second together, i.e., put in the Justice Brothers, drive to the workshop and used the shell engine flush.My car is still running ok.Benefits - super clean oil, very little specks of carbon seen on the dipstick and this condition lasted for at least 2000km. After that, its back to normal.Car definitely felt lighter after the flush. One of my friend lives by a variation on the third way. He changes oil every 3,000km.Your car, your choice.