The 1990s weren't exactly a golden era for Mercedes, at least as far as reputation went. During this period of time, Mercedes was undergoing a few managerial and ownership changes that put the bean-counters in charge of the engineering department, and stockholders in charge of product development. While mid-1990s cars like the E320 weren't particularly bad in and of themselves, keeping up on basic maintenance like oil changes could go a long way toward avoiding some pretty costly repairs later.
Mercedes was one of the first manufacturers to use a "legitimate" oil life monitoring system that used a mathematical algorithm and information from the engine's sensors to determine the condition of the oil and notify owners when it was time for a change. The Mercedes system defaults to a 10,000-mile interval, and subtracts mileage at a faster rate when the car is driven in harsher operating conditions. Lots of stop-and-start traffic, short trips, full-throttle and high-load driving, very high or low temperatures and other conditions will wear oil out faster, causing the oil clock to wind down quicker.
Look to the left of your instrument cluster, and locate the "0" button that resets your trip odometer. To reset the reminder, start by turning your ignition key to the "On" position without starting the engine. Within four seconds, press the "0" button twice; you'll see the status display for days or distance. Within 10 seconds, turn the ignition key to the fully "Off" position. Press and hold the "0" button while turning the ignition key back to the "On" position. You'll see the day or distance display again. Keep holding the button for a further 10 seconds until you hear a chime, and the display reads "10,000" miles for approximately 10 seconds. Release the button after the 10 seconds has elapsed -- the oil monitor is now reset.
You just need to add coolant to the coolant reservoir tank under the hood until it's at the "cold" fill level while the engine is cold. This will turn the light off. The Mercedes takes Pentosin coolant, a silicate-containing coolant that doesn't mix with other types.
