2002-2006 2nd Gen Audi A4 Sedan, Avant, and Cabriolet Maintenance and Cost
The Audi A4 B6 isn't a particularly problematic vehicle to service and maintain unless something big goes wrong, and except for the fact that both Audi A4 engine derivatives need to be rigorously maintained. Replace the engine oil with good-quality synthetic oil every 5,000 miles and change the filter at the same time. Good-quality oil is the lifeblood of an Audi engine, and compromising on this will lead to tears.
For vehicles equipped with the Multitronic CVT, a transmission oil change and filter replacement every 30,000 miles are required to give it the best chance at survival. The five-speed automatic transmission in the 1.8T quattro and the six-speed automatic in the 3.0 quattro are both capable of a fair service life, provided their transmission fluid and -filters are replaced every 60,000 miles at the latest.
Spark plugs should be replaced every 40,000 miles according to the 2002 Audi service schedule, but we'd recommend replacing them every 30,000 miles instead. Doing so should make it easier for the failure-prone ignition coils to provide a stronger spark for a longer distance. Ensure that the heat range of the spark plugs are as prescribed by Audi, because fitting inappropriate spark plugs could lead to pre-ignition and, consequently, internal engine damage.
The engine air filter also has a 40,000-mile replacement interval, but don't hesitate to shorten this to 30,000 if your vehicle is operated in dusty or polluted conditions. Pollen filter replacement intervals are set at 20,000 miles, and the same advice regarding dusty conditions applies.