Volkswagen’s Turbochange Direct Injection (TDI) clean diesel engine offers high mileage between fill-ups and more than 50% better fuel economy than similarly sized gasoline engines. With a potential 43 highway miles per gallon, you can get up to 795 miles per tank, in a car that emits lower CO2 commissions than 93% of other vehicles. TDI is available in newer Volkswagen cars such as the Passat, Golf, Jetta sedan and Sport Wagon, Beetle and Beetle Convertible, and Toureg.

To keep your tdi running at peak performance, it’s important to understand how it works and how to maintain it.

What makes a TDI engine different

The secret of TDI’s success lies in engineering. Replacing the indirect injection of older diesel models, the new models use a fuel injection system that sprays atomized fuel directly into the main combustion chambers and not the pre-combustion chambers. This process is combined with forced induction with a turbocharger that increases the amount of air passed into the engine’s cylinders and an intercooler to reduce the temperature and density of turbo charge air.

The result for you, the buyer? More fuel is injected and burned, so you’ll notice increased engine efficiency and increased power, along with more torque and lower emissions.

Fuel Requirements for TDI

The Volkswagen Tdi engine runs on diesel fuel (petrodiesel) or certain types of biodiesel fuels. The downside of the engine’s technical PROWESS is that it is picky about the type of fuel it needs. In the US, VW recommends #2 diesel fuel which has a higher cetane number than #1 fuel and a lower viscosity. Proper fuel straight from the pump is common in Europe, but some American drivers must use additives or premium diesel to ensure correct cetane levels.

“Misfeeding” your Tdi engine with regular gasoline instead of diesel can be a costly mistake. Older Vw models WERE MORE forgiving but putting the wrong fuel in the modern Tdi engine will damage the fuel pump and ruin the engine when the fuel goes through the fuel system. That system on 2013 vehicles has been redesigned with a fuel tank flap to prevent you from inserting a gas nozzle instead of a diesel nozzle into the tank.

The cost of an accidental incorrect refueling can range from $100 or so to pump the wrong fuel and replace the filters to over $8,000 to replace the entire fuel system. Most of these repairs are not covered under warranty.

What can you diagnose yourself?

Local Your Vw dealer has a great service department that can keep your tdi engine running strong. Regular maintenance costs run about the same professional service for a VW gas engine. However, if you have a backyard mechanic who enjoys making his own car, there are a few situations unique to a tdi that you can diagnose yourself:

• If you listen to noise, are they “normal” in your TDI engine? Most drivers notice steering column clicks, farm and pressure control valve clicks, and a hissing noise from the shoulder valve when the engine is turned off. These noises indicate proper performance, not a problem, but as a new TDI owner, you need to learn what to ignore and what to pay attention to.
• Engine won’t start or won’t start? While the car is in neutral, turn the ignition to the run position to see if you get a check engine warning or glow plug lights. If not, you may need a new battery as the motor is not receiving power.
• Does the engine start? If you see the check engine or glow plug lights on the dash, but the car makes noise when you try to start, you may have low fuel, corroded cables leading to the battery, or loose connections.
• Do you get a “relay 109” fault? If your check engine light or glow plug goes on and off, you may have a 109 relay fault that requires replacing the relay. If that doesn’t work? You may have a faulty ignition switch or security system. You may also see the glow plug light if you have a burned out brake light.
• Does your engine smoke when revving to full throttle after a fill? You may have received a poor quality fuel tank.

A Volkswagen TDI engine offers the best in performance and efficiency, but they are particular engines that require very specific maintenance and repairs. Always remember to replace faulty parts with genuine volkswagen replacement parts, or choose your local vw service for professional service from experienced, certified mechanics.