To let drivers know when to change out their engine oil and filter, many modern vehicles have incorporated fuel and mileage data from the powertrain computer, used by the Driver Information Center (DIC). This calculation factors in driving habits (such as city vs. highway) as well as acceleration and load tendencies. In other words, "lead footed" city drivers will see their oil change indicator light illuminate more frequently than conservative highway drivers.
For many years, the standard oil change interval was 3 months or 3,000 miles, whichever came first. By one of these intervals, engine oil had either broken down from the mechanical wear of the engine components or had been fuel saturated due to the inefficiency of carburetors, which tended to overfuel engines. Much of this fuel wasn't properly burned and would leak down the sides of the cylinder walls and into the oil pan. After about 3,000 miles or 3 months, the engine oil accumulated so much fuel that its ability to provide lubrication protection to the moving components in the engine was severely compromised.
As fuel injection replaced carburetors in vehicles, the amount of wasted fuel began to decrease dramatically. This was accompanied by more sophisticated engine management systems that increased the engine operational temperatures, allowing efficient combustion to occur with ever leaner mixtures (less fuel per portion of air).
And, as the price of crude oil increased over time, most vehicle development focused on smaller engines with fewer cylinders and smaller components (smaller in both size and weight). This meant that the viscosity of the engine oil—its thickness—could be decreased. Manufacturers discovered that these positive changes were having an effect on engine oil life. The typical breakdown of viscosity, usually reached by 3,000 miles or 3 months, wasn't occurring and the oil change intervals recommended by the vehicle manufacturers began to increase from 3,000 miles to 5,000 miles to 10,000 miles and beyond.
Vehicles equipped with a messaging system will see an oil life of 10 to 100 percent displayed in the center of the dash that should go off in 1 to 5 seconds. If the oil life is at or near 0 percent, the messaging system will display an "oil change due" message. Typically, until the oil and filter change is performed and the oil life messaging system reset, the light will continue to display.
What to Do: Oil Change Indicator Light
On vehicles with an oil change light, an oil change is needed when the light remains on after startup. It is best to schedule the oil change within one to two weeks, depending on the type of driving that will be done. If it's highway driving, you have a little more breathing room than city driving. If a trip is scheduled, have the oil and filter changed before leaving.
Vehicles with an "oil change due" messaging system will display a message when there is less than 10 percent oil life remaining. When this message displays, the next oil and filter change should be scheduled within one to two weeks and before any substantial driving trip.
Whichever indicator your vehicle has, always have the repair shop reset the oil change indicator after completing the oil change. You should also request that an oil change reminder sticker be attached somewhere on the vehicle that states when the next oil change is due in terms of mileage and time as well as what type of oil and viscosity to use. The oil change reminder sticker provides technical information to the repair shop performing the oil change and also keeps track of the accuracy of the oil change light system itself.
At a minimum, you should check your oil level at every other fuel fill-up or once a month. If you do not know how to do this, have the repair shop that performs the oil change check it. Even a dealership should be willing to do this for regular customers. This service should not require an appointment, nor should you be charged for it. Vehicle owner's manuals typically have good instructions with diagrams showing how to check the oil level, as well as other fluid levels.