Oil and filter changes are one of the cheapest and most effective ways to prolong the life of your car. Almost any mechanic or repair shop can perform one for you. Pricing varies significantly based on the type of motor oil your car requires, as well as your location.
How Often Do I Need an Oil Change?
An oil and filter change should be performed on a regular and strict schedule. The car’s owner manual and the electronic indicator on the dash are good starting points for when to change your oil. Depending on the manufacturer, this interval can range from 5,000 miles to 7,500 miles. These recommendations are based on normal driving conditions.
Most cars are actually driven under severe or varied driving conditions — extreme temperatures, higher speeds, and constant idling in traffic. Proper oil viscosity (thickness) is much more important under these operating conditions, but these conditions break down the viscosity more quickly. Therefore, for the majority of cars on the road, a 3,000 mile interval for conventional oil and a 5,000 mile interval for synthetic oil are a safer bet.
Oil changes for aging cars should become more frequent. As engines age, many gaskets and seals used to hold the oil inside the engine become dry and porous, allowing oil to leak. Also, as moving parts wear, particularly the cylinder rings, oil will pass into the combustion chamber and be burned. These worn parts also allow unburned fuel into the oil, which thins it out, making it less effective.
Why Are Regular Oil Changes Important?
Engine oil is your cars most important fluid. It performs three major functions in today’s modern engines:
Oil provides critical lubrication to the multiple moving parts within the engine, especially the valve train, where metal to metal rubbing is constant. This decreases the friction between two metal moving pieces, which in turn keeps the engine from creating too much heat.
Oil carries away dirt, grime, carbon and metal particles before they can build up and wear engine parts. These contaminants are suspended in the oil until cleaned out by the oil filter.
Oil feeds many small switches in the car. When the oil pressure increases, these switches change valve timing (variable valve timing), which allows for increased fuel economy, decreased emissions and good power throughout the full torque spectrum.
What If I Don’t Follow The Recommended Intervals?
Infrequent oil changes can cause a variety of engine performance issues, and eventually lead to catastrophic engine failure. Engine oil is designed with special viscosity (thickness) properties, so that it can be thin at motor startup to provide instant lubrication, but also retain a prescribed thickness at running temperature in order to provide good lubrication and heat dissipation.
Oil begins to break down over time, retaining moisture and grime as the filter becomes more clogged. The oil becomes thicker at startup temperatures and thinner at higher temperatures. At this point, if neglected, the oil becomes a sludge or gel-like substance. This sludge cannot move through engine passages very well, leaving many critical parts starved for lubrication.
When the oil thickens, valve train switches don’t receive the oil pressure required to change timing. Fuel mileage drops; emissions rise sharply.
These types of problems can occur in cars with as low as 40,000 miles. Many manufacturers now require regular oil changes to maintain engine warranties.
Service article originally written by an ASE Master Technician