Ah nice thanks everyone for the replies looks like I will be lookin into a TDI. How good do those motors last with good maintenance?
Also just out of curiosity using a small car as a commuter, when ya hop back in your truck, does it feel like your truck is massive?
The ALH TDI engine in most of the Mk4 Jetta and Golf TDIs is very reliable, with most of the TDI guys considering it something similar to a 12V Cummins... There are a lot of aftermarket parts and support available for the ALH engines.
The PD TDI engine in the late Mk4s (03-04 I believe) and early Mk5s (until 06) have cam wear issues, but Colt makes an aftermarket cam that is stronger and it can be changed pretty easily when doing the timing belt. Not as much support for this engine here in the US as it was only used for a few years.
Speaking of timing belt, it is a good idea to change it soon on any new TDI purchase (unless they show receipts that EVERYTHING was properly changed including the idler pullies, water pump and such) since they are interference engines and a broken belt or even seized idler will likely damage the head and bend valves...
You can probably incorporate that into the purchase price, figure on $1000-2000 for parts and labor having just the timing belt done and having it done with the cam/lifter replacement.
Some of the CR ('09 and newer) TDIs have experienced high pressure fuel pump failure, but many seem to be attributed to misfueling or low quality fuel. The CP4 that they use does not protect the rest of the fuel system when they fail and debris goes through the injectors and the rest of the fuel system... It can be an expensive repair! There is at least one aftermarket kit that is supposed to protect against damage to the rest of the fuel system. The CRs also have more power, but with that also a little bit lower mileage.
Either way you should be able to find a nice car for way less than your $15-20k budget with a Mk4 or Mk5 VW TDI and they should last you MANY miles!!! I've heard of them lasting well into the 200,000 and even 300,000 range.
http://www.tdiclub.com is a good source for TDI info.
We paid $4500 for Kyle's 01 Jetta about 7 months ago and it had pretty low mileage and was in pretty good shape. We paid $12,500 for our 06 Jetta about 4 years ago and it had low miles and was in good shape...
I'm comfortable driving my '06 Jetta TDI which is also lowered and carving corners in it, then hopping into my lifted long-travel '01 Duramax truck with no problems. They couldn't be much more different!!! You get used to the differences.