What Is the Importance of Oil in a Car?. Cars require oil as a means to lubricate and cool engine components. The importance of clean oil that contains the correct viscosity at operating temperatures for a specific engine maintains engine performance and life. Oil is a relatively cheap preventive maintenance product, compared to the critical engine components that can fail as the result of dirty oil, lost viscosity and low oil crankcase levels. Every vehicle owner should pay strict attention to the manufacturer's recommended oil change intervals, the specific viscosity and types of oil prescribed for the car.
Most cars have a dash warning light or a mechanical oil pressure gauge that alerts the driver of a low oil condition, oil pressure difference or a regular oil change interval. A "Check Engine" light also might serve this purpose, depending upon the year of the vehicle. It is important to respond immediately to such a warning light or low oil pressure reading. Under normal driving conditions, a vehicle owner changes the oil every 5,000 to 7,000 miles, every six months or according to the owner's manual specifications. Older engines can benefit with changes more frequently, from the 3,000- to 5,000-mile range, since oil contamination occurs sooner in older engines.
Oil viscosities of 10W-30 and 10W-40 are two of the most commonly used oils. The 10W-30 classification has a lower cold-start viscosity, allowing for flow at cooler temperatures, as indicated by the "W," which stands for "winter." The 10W-40 is a thicker blend reserved for summer months or higher temperatures, but carries a 10W for the cooler temperature ranges. Oil with a 5W-30 rating is used at or near freezing temperatures when starting the vehicle. Multi-viscosity oils, such as OW30, 5W30 and 10W40 are used when temperature fluctuations are extreme, with frequent dips from highs to lows. Multi-viscosity oils automatically adjust to the variations in temperature according to their range. Almost all automobile vehicles use detergent oil, which have additives to combat alkaline, rust, moisture and acids.
All quality motor oil forms a thin film between moving components in your car engine for lubrication purposes. Such components include piston rings, crankshaft bearings and races, camshaft bearings, valve stems, piston pins and connecting rods. The oil film disallows contact between two mating metal surfaces, permitting them to slip or glide by each other; thus, oil acts as an insulator between moving parts. In places where no friction results, the engine rpm increases without undue strain on the engine.
Oil that circulates through block passages, oil valleys and bearing surfaces picks up engine combustion heat and transfers it to cooler areas, such as the oil pan. The oil pump produces pressure to circulate the oil from oil in the pan, keeps the oil flow in constant motion, never allowing it to accumulate in the hottest regions of the combustion area. By transferring high internal combustion temperature, oil has a cooling effect on the engine and promotes better overall performance. Oil coolers, which come standard on many vehicles, lower the oil temperature even farther, extending the life of the oil and keeping it within proper viscosity ranges.
Detergent oil has specific additives that break down and latch onto sludge, particulates, rust, moisture and acids. Detergent oil breaks down carbon, exhaust gases and soot in the combustion chamber so they do not adhere to the metal surfaces. The foreign matter is trapped in the oil filter, which keeps the contaminants from re-circulating throughout the engine. This self-washing process extends the life and quality of the oil, lengthening the time between oil changes, and lubricates engine parts at the same time.
Good quality oil acts as a noise damper in automotive engines. Besides the thick coating oil provides over major parts to deaden the sound, it eliminates unneeded friction and vibration between hard metal parts. For example, hydraulic valve lifters are prone to noise when the quality of the oil has been compromised or when oil level is low, resulting in the common "clacking" or "clicking" sound. A quiet, smooth-running engine results from oil providing the proper barrier between moving parts.