1990 Mercedes-Benz 420SEL Oil Change Cost

It is possible to drive a vehicle without an oil change, but driving a vehicle after the specified service interval has passed is not recommended. Over time engine oil breaks down from use and is contaminated by the combustion process (blow by gasses). The oil and filter should be changed as soon as is convenient to maintain protection of internal engine components.

Oil should be changed regularly to prevent internal engine damage and breakdown. Manufacturers differ in their recommended guidelines for how often to change engine oil and oil filters. The traditional rule of thumb is that engine oil should be changed every 3,000 miles to keep the engine healthy and to prolong its life. Most modern cars do not require the old "3 Months or 3000 Mile" service interval. In some cases it is several times that, but at least once a year is recommended, no matter how little you drive. Some cars are also equipped with maintenance computers that let you know when the oil life is depleted, or when the specified maintenance interval has passed. This notification can come on more often depending on environment or driving conditions such as towing, or long periods of stop and go traffic.

To change the oil, a technician allows the engine to cool down, then removes the drain plug at the bottom of the engine oil pan and drains the oil. As the oil is draining they will remove and replace the oil filter. When the oil has fully drained the drain plug is re-installed and the engine is filled with the proper type and amount of new oil. The engine is started and checked for leaks. Finally, the engine is switched off, the oil level rechecked, and the maintenance light reset. While the oil is being serviced, the technician will note any obvious issues with the condition of the engine seals, amount of oil drained, last service date and mileage, and the drained oil's condition. If any abnormalities are noticed, recommendations for diagnosis or repair are made. Most manufacturers have now included panels that are attached to the vehicle's underside; they offer a measure of protection from debris and a means of controlling air flow to the engine and around the vehicle. These panels often completely cover the engine/transmission from below, blocking all access. Removal of one (or more) of these panels and their correct re-installation adds two new steps to the process of an oil change.

When changing or adding engine oil, follow the manufacturer's recommendation for the grade, often referred to as "weight" (0/30W, 5/30W, 20/50W, etc.), and type (petroleum or synthetic base) of oil to use. The grade is based on the oil's ability to flow - "viscosity". Modern engines are especially sensitive to the kind of lubricants used. Using an incorrect type or grade can cause the oil pressure light to illuminate, the engine to make abnormal noises, the check engine light to come on and may invalidate your manufacturer's warranty. So, always ask what oil you are getting, and know what is recommended for your car. Consulting your owner's manual is the best way to ensure you are using the correct fluids for your vehicle.

An engine oil change can be performed by intermediate DIYers. However, before attempting this service or ordering parts, be sure to look up the specifications and procedures for your particular vehicle. Most will require raising the vehicle to access the oil pan drain plug, and it is critical that the oil is refilled to the proper level, and that the oil filter is installed correctly. If there is any concern about completing this service properly, consider contacting your local RepairPal Certified shop.