Auto Repair Encyclopedia
Oil Change Indicator Light
Many modern vehicles have incorporated fuel and mileage data from the power train computers, used by the driver information center, to calculate the optimal time and mileage interval to replace the engine oil and filter. This calculation is able to factor in driving habits such as city vs. highway as well as acceleration and load tendencies. In other words a 'lead footed' city driver will see their oil change indicator light illuminated more frequently than a conservative highway driver.
For many years the standard oil change interval was 3 months or 3,000 miles, whichever came first. Usually by one of these intervals most conventional engine oil had either broken down from the mechanical wear of the engine components or had been fuel saturated due to the inefficiency of the old carburetors that tended to over fuel engines. Much of this fuel wasn't properly burned and would leak down the sides of the cylinder walls and into the engine oil residing in 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 seriously compromised.
As fuel injection replaced carburetors in vehicles, the amount of wasted fuel began to decrease dramatically. This was accompanied by more and 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 as well as 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.
When the engine is first started the oil change due light should come on for 1-2 seconds and then go out. A light that stays lit indicates that the vehicle is due for an oil and filter change. Vehicles equipped with a messaging system will receive an oil life of 10-100% displayed in the center of the dash that will go off in 1-5 seconds. If the oil life is at or near 0% an oil change due message will be displayed. In some cases this message will remain displayed until the oil and filter change is performed and the oil life messaging system reset.
What to Do: Oil Change Indicator Light
On vehicles with an oil change light, the oil change is needed when the light remains on after the vehicle is being operated. It is best to schedule the oil change within 1-2 weeks depending on the type of driving that will be done. If a trip is scheduled, by all means, have the oil and filter changed before leaving.
Vehicles with an oil change due messaging system will display a message when there is 10% or less oil life remaining. When this message displays the next oil and filter change should be scheduled within 1-2 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 and 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.
Note: The oil level should be checked at every other fuel fill-up or every month at a minimum. If you do not know how to perform 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.
