Thought I would point out, if the Jetta has a 1.8T engine, synthetic is a must have. The turbo in that engine can run very hot if driven hard, synthetic can run hotter without cooking and turning to sludge, as opposed to regular oil. I have a 1.8T in an Audi, and the general consensus seems to be that synthetic changed at an interval at less than 5,000 miles should be done. Also, the biggest oil filter available should be used to help keep the oil cool. It is also important with that engine to let the engine idle for 1-3 minutes if the car is driven very hard, to allow oil to circulate and cool the turbo. However, if the engine is the 2.0 or a non turbo engine, synthetic isnt as critical, but might still be recommended.