Oil Changes
In a perfect automotive world, there would be no metal-to-metal contact between parts in an engine. In fact, this is the purpose of oil in the vehicle’s engine. Oil molecules adhere to parts like pistons, cylinders, bearings, crankshaft journals, camshaft lobes and followers. Oil prevents parts running against one another creating wear, friction and wasting fuel. Modern lubricants can allow the engine to run efficiently, reliably and powerfully for hundreds of thousands of miles.
As one lubricant manufacturer says in their advertisements, “think of oil as microscopic ball bearings”. A more accurate analogy would be spaghetti. Oil is composed of long chains of hydrogen and carbon atoms. These long chains act like long strands of wet spaghetti. If you put long strands in a colander in the sink, it is difficult to get them to fall through the holes in the colander. If you cut the spaghetti into short pieces, they pass through the colander easily. The thickness or viscosity of oil is the result of these long hydrocarbon chains intertwining with one another and causing the oil to move more slowly than less viscous liquids. Over time, in an engine, oil is subjected to shearing which cuts the long chains and reduces viscosity. This is the main reason why oil changes are a necessity.
When oil loses viscosity enough to drop out of its viscosity range, it should be changed. You do not need to know exactly when this happens. Just follow the suggestion from the “service oil soon” light on your dashboard.
Modern oils also contain detergent and friction modifier packages which are also used as the vehicle is driven. The detergent surrounds small amounts of carbon soot and holds it in suspension so that it is removed at oil change time. When oil is left in an engine for long periods of driving, the carbon soot can begin to form sludge which is very difficult to remove without physically dismantling the engine and mechanically cleaning the parts. Though these are all secondary reasons for oil changes, oil must survive very high temperatures and is exposed to products of combustion in the crankcase. Give your engine a break and make certain it has clean oil at regular intervals.
Most vehicles today have onboard diagnostic software to remind the driver to change the oil. The oil change interval doesn’t depend on measuring changes in viscosity or impurities in the oil. Oil change intervals are based on an algorithm that modifies the change interval by the way you drive. Freeway driving at a constant speed, with the engine completely warm is the lowest friction, stress and challenge your engine and its oil ever experience. Stop and go driving with extreme acceleration when engine and oil are cold puts the highest stress and wear on the engine. The oil change reminder software integrates the time spent under low and high stress conditions and lengthens the intervals when much of your driving is on the freeway and shortens the interval when the vehicle is used in traffic on short trips. Pay attention to the service engine light. By changing the oil based on its recommendation, you will spend the absolute minimum on oil changes commensurate with maximum engine life and minimum maintenance cost.
Most engines require about five (5) quarts of oil. Modern manufacturing and machining methods mean that most engines will consume less than a pint between oil changes. However, when an engine is run with the crankcase oil level more than three (3) quarts low, it is possible for oil to move away from the oil pump pickup as the vehicle goes around turns. When this happens, air can be entrained in the oil as it is sent to bearings. At 2500 or 3000 RPM oil starvation at the bearing can do permanent damage which is very expensive to repair. The best defense against expensive oil starvation damage is simply to check the oil on a weekly or monthly basis.
The best oil for your engine is that recommended by the owner’s manual. Without the owner’s manual, you can consult the internet. When checking the oil, the vehicle should be on level ground. The oil level should be between the maximum and minimum marks on the dipstick. If the oil is below the add mark, and you don’t know what oil to buy, always remember, any oil is better than no oil at all. Any oil that is certified by American Petroleum Institute (API) marked as motor oil and sold at an auto parts store, is fine. One quart is only 20% of a five (5) quart oil pan. You don’t need to be too concerned about the viscosity or whether the oil is conventional or fully synthetic. These issues are immaterial when you are far away from home and your vehicle is low on oil.
There are two basic temperature conditions seen in a modern vehicle’s engine. When the temperature is very cold such as below zero (0) degrees Fahrenheit, conventional oils are much thicker, difficult to pump and can cause oil starvation of the engine when started cold. At high temperatures, above one hundred degrees (212) Fahrenheit, the same oil can lose viscosity reducing oil film maintenance in bearings and between pistons and their cylinder walls. Modern oils are multi-viscosity which means they are chemically engineered to be different thicknesses depending on the temperature. At low temperatures the oil molecules contract, the long hydrocarbon chains becoming a coil, resulting in shorter chains that perform as a lower viscosity oil. The viscosity, therefore, becomes lower, making the oil easier to pump. When oil temperature reaches one hundred and ninety (190) degrees Fahrenheit, the long hydrocarbon chains become uncoiled, and the oil becomes a much higher viscosity. This multi-viscosity oil will come with a number marked on its container such as 10W-30. This means that when the oil is about thirty-two (32) degrees Fahrenheit, it will behave like a 10-weight, low viscosity oil. At two hundred (212) degrees Fahrenheit the oil will become a 30-weight, higher viscosity oil.
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