Found this and it looks like it is noy just mileage based
The Ram Oil Change Indicator system is not a simple oil quality sensor, but a software-based, algorithm-driven device that takes into account various operating conditions of the engine - the engine size, engine revolutions, and even ethanol levels in the fuel - to determine when the oil needs changing. That said, the computer does not strictly track mileage or the condition of the oil, but also tracks certain driving habits that can affect the life of the oil, as well as driving conditions such as temperature and driving terrain. Lighter, more moderate driving conditions and temperatures will require less frequent oil changes and maintenance, while more severe driving conditions will require more frequent oil changes and maintenance. Read the table below to see how the Oil Change Indicator system determines oil life.
- Note: Engine oil life is dependent not only on the factors listed above, but also on your specific vehicle model, year, and what type of oil is recommended. Check the owner’s manual for more information about what oil is recommended for your vehicle, and don’t hesitate to get in touch with one of our experienced professionals for advice.
Some Ram models have a percentage-based indicator that counts down the oil life as a percentage. Once the information display number reduces from 100% (fresh oil) to 15% (dirty oil), an “OIL CHANGE REQUIRED” light will be trigged on the dashboard information display, giving you ample time to
plan ahead to have your vehicle serviced. Every time you start the engine, the engine oil percentage will be displayed. When the information display number reaches 0%, the oil life is over and you begin accumulating negative miles that tell you your vehicle is past due for servicing. Remember: if the vehicle racks up significant negative mileage, the engine is increasingly at risk of damage.