Why is it necessary to change vehicle oil regularly, and not just change the filter and add new oil as needed?
In: Engineering
Engine oil needs to have a special amount of gooeyness so it can stick to and stay between moving parts.
This gooeyness (what boring people call viscosity) decreases with temperature.
This means engine oil is like honey when cold and like water when hot.
There are additives which change how engine oil responds to temperature, allowing the same type of oil to be used summer and winter.
Over time these additives chemically transform, becoming ineffective.
When you change a car’s engine oil, the oil you are removing has used up its additives and the oil you are putting in has fresh additives.
I like to explain the importance of changing oil in terms of sex.
Imagine penetration without adequate foreplay. Ouch!
In most cars, you have to drain the oil to change the filter in the first place. Because if you don’t, the oil will drain out of the space where the filter is supposed to go.
You can do that short term, but eventually you have to do a complete change. When I drove 3-4 k a month, I would change the filter every month. I would do a complete change,with filter, at 30k to 40k miles. This was on Chevy Astro vans and a Ford Flex. They all went over 200k miles, with no problems. I only used full synthetic oil.
The filter just picks up solids, usually in the form of tiny specs of metal that occur from normal wear. These particulates just happen to be suspended in the oil, which makes it convenient to filter them out so they don’t cause any more problems.
The oil itself has a couple jobs, but the primary one is to lubricate the moving parts so it’s not metal on metal grinding. The oil also has additives that the internals of your engine like, and your engine will gobble them up during normal operation. Your oil also has detergents in it to keep things clean. Another lesser talked about function is that it does actually help with heat dispersion. All of these properties deteriorate over time. Oil that’s been heated and cooled back down many times loses some of its lubrication properties, the additives run low, and the detergents have run out. Eventually you need to replace it with fresh oil.
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