Originally posted by Riflesmith
IMHO, the VW TDI’s are the best kept secret in North America. My wife and I purchased a New Beetle TDI in March of this year. It has marvelous low end torque and laughs at hills. The AC is ice cold and has no impact on performance. We average around 48 MPG with mixed 65-75mph highway and 80mph freeway driving. The Jettas and Golfs will average slightly higher MPG since they are more aerodynamic. This is with a five-speed. The automatics get around 42 MPG.
There are some things the cars have I take issue with:
1. Cooled EGR. This system takes exhaust from the pre-turbo area of the exhaust manifold and pipes it through a cooled manifold and enters the intake downstream of the intercooler. The EGR valve can be defeated, but it is difficult to prevent the ECM from seeing this because it increase the total air flow across the mass air flow sensor. The best way to defeat the EGR is by changing the air flow demand value in the ECM using a computer program called VAG-COM. This keeps the EGR valve closed without triggering a check engine light and fault code.
2. Closed Crankcase Ventilation. The crankcase blowby gases are routed directly into the intake airstream upstream of the turbo. These oily vapors contaminate the compressor and intercooler, then they combine with the soot entering the intake air stream from the cooled EGR. This forms, over time, a carbonaceous, clogging mess that is difficult to clean up. This can be avoided by routing the blowby overboard, like the Cummins.
3. Timing belt. Keeps the engine noise down, but requires periodic changing. Current models have the longer 100K mile change interval. It is very expensive to have this done at the dealership. It can be done by the do-it yourselfer.
Sorry for the long post. I paid $600 over invoice for mine at a dealership in Sandy, UT.
A good post, sums up most things but not entirely accurate. The EGR is equally or MORE responsible for the intake clogging than the CCV. Either running the EGR by itself or the CCV by itself is fine. It's the COMBINATION of the sooty EGR exhaust and the oily CCV mist/vapor that form the hard carbon. That said, I still modified both on mine
.
The check engine light that results from removing or disconnecting it can EASILY be defeated. It's called an EPS device, and installs in 5 minutes. I did this to my TDI, and it was smooth sailing(clean intake) since. I can point you in the right direction if you want one of these devices, but be aware these are for 'off road' use only, as modifying emissions equipment is illegal.
Jetta's and Golfs might be slightly more aerodynamic than the beetle, but the beetle has slightly different gearing. They all get similarly good MPGS.
Commonly known TDI problems - POS MAF sensors that WILL go bad, window regulators, weak clutches, and tons of rattles. If you can live with those, they are great little cars. The clutch is only a problem if you start modifying it. 2000. 5+ TDI's switched from a LUK to a Sachs clutch, which only has a holding strength of 200 lb/ft of torque. Stock TDI's make 155lbs, but a chip puts it right near or over 200, depending which model you go with, causing slip.
Timing belts are only do-able by the do it yourselfer if you have SIGNIFICANT mechanical skills and tools - not for the shade tree mechanic who does oil and filter changes... . beware!
Lastly, a/c DOES have a major drag on performance, Riflesmith must be floating in ignorant TDI bliss!!!
Try running at a constant speed, say 2000rpm in first gear, and click on the a/c. WOW, what a drag. The mpg suffers as well... this is clearly evidenced with VAG-COM..... if you don't believe me, go to the fields where it shows fuel consumption, and injection quantity at idle, and turn your a/c on and off... . the extra fuel draw is significant - about 2mpg. Then again, when you get 50mpg, who cares if you get 48!!!
I would however, recommend TDI's to anyone who wants a high efficiency, comfortable, and surprisingly peppy commuter. I will say, stock 90hp TDI's are way too slow for my taste/patience. Before I chipped mine, I had to floor it to keep up with the grannies in their crown vic's and town cars down here, they really step on it. The chips are usually swappable, I'd put the stock chip back in when I took it to the stealership, and it is PAINFUL to drive a stock TDI. Beware - 0-60mph on a 5spd is about 10 seconds, and autos are around 12 seconds... . The torque fools you because it feels fast, but they are slow as hell. Once you set them up right, they are fun. I highly recommend Dieselgeek's short shift 'race' kit. I had it on my tdi, really shortens the throws, and you can hit 5th with your arm still on the armrest
Attention: TDR Forum Junkies 
I was just trying to help and clarify. I didn't think being thick skinned was necessary, my post was in no way to discredit your info, just clarify and expand. . 
