I've been convinced of the benefits of diesel engines from working on and driving my brother's TDI Passat. The combination of power and fuel economy is simply impossible to achieve with a gas engine; that thing has 247 lb-ft at 1800 RPM from a 2.0L 4-banger (stock, also I think 140 HP?) and gets up to 45 MPG on the highway, with a conventional auto trans to boot. It's also at 225k miles and runs like new (the engine, the rest of the car has been slowly starting to fall apart the past couple years lol).
With JUST a tune, no actual upgraded hardware, you can easily get an extra 30 HP and 70 lb-ft from those TDIs. Can't really do that with an N/A gas engine.
