08-05-2020, 10:40 AM
Detergent oils were developed to solve the problems experienced on diesel engines, piston rings stuck in their groves with carbon build up, valves sticking for the same reason and oil changes were done with a shovel. In the 1950s attending to an engine for an oil change would reveal the sump full of sludge with troughs cut in it by the cranks, the whole lot had to be shovelled out. I can remember in the mid 1960s doing piston exams on marine diesels which ran on diesel fuel, we could have a piston out in an hour or so then it would take the rest of the day to clean the ring grooves of the carbon build up. Today a similar engine running on modern oils and residual fuel oil, which resembles tar when cold, and the pistons are wipe clean. Detergent oils keep the carbon in suspension to be removed by a filter, which we don't have, so regular oil changes are the order of the day. I do my oil changes when the oil is hot immediately after a long run so that there is less risk of the clag settling out.