Oil Life Monitor Systems

From the 1970s until the mid 1990s, the standard oil change interval was “change your oil every 3000 miles or every 3 months, which ever comes first”. This included all makes and models of cars and light trucks. Then, in the mid 1990s, vehicles started to incorporate automatic ‘oil change is due’ reminder systems that were based on several computer generated criteria.

Vehicle systems tracked the number of gallons of fuel consumed and when that total reached a specified threshold an “oil change is due’ message was displayed in the instrument cluster on vehicle start up. Vehicle systems deploy a sophisticated oil viscosity measuring device installed inside the engine oil pan that follows the rise and fall of a flotation device that changes its height as the oil heats up and expands and then as the oil cools down and contracts. When this rate of viscosity change reaches specified criteria, the driver is alerted that an oil change is due. Other systems track the amount of miles driven at city speeds versus the amount of miles driven at highway speeds

And many of the most sophisticated systems use all of these tracking criteria simultaneously to calculate the time and or mileage when an ‘oil change’ is due. There was one result that all of these systems created. They all extended the time and mileage between oil changes. Some extended the interval from 3000 miles to 10,000 miles or more, while some of the most modern vehicle systems are designed to only require a single oil change per year.