The oil and the oil filter need to be periodically replaced.
In engines, there is some exposure of the oil to products of internal combustion, and microscopic coke particles from black soot accumulate in the oil during operation. Also the rubbing of metal engine parts produces some microscopic metallic particles from the wearing of the surfaces. Such particles could circulate in the oil and grind against the part surfaces causing wear. The oil filter removes many of the particles and sludge, but eventually the oil filter can become clogged, if used for extremely long periods.
The motor oil and especially the additives also undergo thermal and mechanical degradation, which reduce the viscosity and reserve alkalinity of the oil. At reduced viscosity, the oil is not as capable of lubricating the engine, thus increasing wear and the chance of overheating. Reserve alkalinity is the ability of the oil to resist formation of acids. Should the reserve alkalinity decline to zero, those acids form and corrode the engine.
Some engine manufacturers specify which SAE viscosity grade of oil should be used, but different viscosity motor oil may perform better based on the operating environment. Many manufacturers have varying requirements and have designations for motor oil they require to be used. In general, unless specified by the manufacturer, heavier weight oils are not necessarily better than lighter weight oils; heavy oils tend to stick longer to parts between two moving surfaces, and this degrades the oil faster than a lighter weight oil that flows better, allowing fresh oil in its place sooner. Cold weather has a thickening effect on conventional oil, and this is one reason lighter weight oils are manufacturer recommended in places with cold winters.
Motor oil changes are usually scheduled based on the time in service or the distance that the vehicle has travelled. These are rough indications of the real factors that control when an oil change is appropriate, which include how long the oil has been run at elevated temperatures, how many heating cycles the engine has been through, and how hard the engine has worked. The vehicle distance is intended to estimate the time at high temperature, while the time in service is supposed to correlate with the number of vehicle trips and capture the number of heating cycles. Oil does not degrade significantly just sitting in a cold engine. On the other hand, if a car is driven just for very short distances, the oil is not allowed to fully heat-up, and contaminants such as water accumulates in the oil, due to lack of sufficient heat to boil off the water. Oil of this nature, just sitting in an engine, can cause problems.
Also important is the quality of the oil used, especially with synthetics (synthetics are more stable than conventional oils). Some manufacturers address this (for example, BMW and VW with their respective long-life standards), while others do not.
Time-based intervals account for the short-trip drivers who drive short distances, which build up more contaminants. Manufacturers advise to not exceed their time or distance-driven interval for a motor oil change. Many modern cars now list somewhat higher intervals for changing oil and filter, with the constraint of "severe" service requiring more frequent changes with less-than ideal driving. This applies to short trips of under 15 km , where the oil does not get to full operating temperature long enough to burn off condensation, excess fuel, and other contamination that leads to "sludge", "varnish", "acids", or other deposits. Many manufacturers have engine computer calculations to estimate the oil's condition based on the factors which degrade it, such as RPM, temperatures, and trip length; one system adds an optical sensor for determining the clarity of the oil in the engine. These systems are commonly known as Oil Life Monitors or OLMs.
Here at Getit Automotive we only use high grade Valvoline oil using the correct grade and specification to suit your vehicle, backed by a nationwide guarantee from Valvoline we ensure that your engine only receives the best at an affordable price.