Why is it necessary to change vehicle oil regularly, and not just change the filter and add new oil as needed?
In: Engineering
Motor oil consists of a base oil and specific additives, such as detergents, dispersants, anti-wear viscosity improvers, corrosion inhibitors, etc.
The base oil lasts significantly longer than the additives do, seeing as it doesn’t really get used up at the temperatures and pressures in most modern engines.
The dispersants deal with sludge which comes from burnt and unburnt fuel slipping past the piston rings and the detergents “wash” the engine, cleaning up varnish and other residuals.
These additives get used over time (due to corrosion and water ingress) as well as ‘miles’ (due to fuel and temperature)
The oil also fills with sludge and soot which can be filtered out when they combine and become big enough, but if you make the filters better so that less soot swirls around, causing wear and varnish, you end up removing the additives also – so there’s a very fine balance to be maintained.
It is definitely possible to sample the oil during a filter change and only add what is needed, but this is more expensive than just changing all the oil at the recommended intervals.
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