How to Improve Jetta TDI Fuel Mileage

1. Drive your Jetta TDI with the purpose of achieving the best possible fuel economy. This means you must, at all costs, resist the urge to speed. Rather, keep your speeds at or below 55 miles per hour. It's also important to avoid aggressive driving. Suddenly increasing or decreasing your speed is wasteful. Keep your speed constant, slow down and speed up gradually.
2. Use your Jetta's overdrive and/or cruise control whenever it is feasible, i.e., on flat, uncongested highways or roads. If you can manage to keep your diesel engine running at a lower RPM, you can help increase its fuel efficiency. If you own a Jetta TDI with a manual transmission, you should attempt to reach your highest gear as quickly as possible without revving your engine too high.
3. Unload excess weight from your Jetta. Look for any unnecessary cargo in the trunk or cabin of your car and remove it. Even an extra 100 pounds will drastically cut into the fuel efficiency of a Jetta, reducing your miles per gallon by as much as 2 percent.
4. Avoid using your Jetta's air conditioner and other accessories as much as possible. Anything that requires extra power will reduce your fuel efficiency as load on your engine and alternator increases.
5. Take your Jetta TDI to a qualified mechanic for a yearly tune-up. Your diesel engine must run smoothly in order to achieve the best fuel mileage possible. A regular trip to the mechanic will ensure that your engine is working as it should. Also, have your oil changed every 3,000 to 6,000 miles, check your air filter and change it if necessary, and inflate your tires to the recommended pressure (you'll find the suggested inflation level on the sidewalls of the tires).
6. Roll your windows up when traveling at highway speeds. At higher speeds, you must ensure that your Jetta is as aerodynamic as possible. Windows that are left down will increase drag and decrease your fuel mileage. With aerodynamics in mind, you should also remove any bicycles or luggage from your roof rack (if equipped).
7. Always fill your tank with quality diesel fuel. It's tempting to go with the cheapest fuel available. This, however, may cost you in the long run. Dirty or watered-down fuel could decrease your fuel mileage and even damage your engine.