The VW Passat
 This guide is as complete as I can make it with the space allowed. It is for 96-97 Passats.

Background information

 A little background info on VW diesels. The first VW diesel that came along that Americans are familiar with is the Rabbit diesel. It was a non-turbo charged engine. It was strictly mechanically injected and produced a small amount of horsepower and was very, very slow. It did however get fantastic fuel mileage, but nobody cared because fuel was so cheap. It was smoky, slow, and small and you had to love diesels to own one. But 50 mpg was nice, even in the late 70's
 Then in the early nineties VW produced an ECO diesel, it had a turbo charger, and was still had a mechanical injection pump. The turbo function on that car was to reduce smoke output and increase the power a bit which is what it did. Power was up, smoke was down, fuel mileage was great, but still it was a slow ride. Gas was cheap, and not many sold.
 In 96 VW introduced a new diesel engine. It was turbo charged, but it had an electronically controlled high pressure injection pump and viola! The legendary VW TDI is born. The electronically controlled pump was the magic! The Jetta was available with a TDI engine from 96 through 99.5. The Passat TDI was only made in 96 and 97 with the TDI engine. (yes VW made Tdi Jetta and Passat in later years, but this guide will concentrate on these earlier more affordable Tdi's) The engine found in these cars is a 1.9 TDI with the engine model designation 1Z. The Passat and Jetta from these years share the same drive train. There are some differences in the engines, mostly plumbing, etc. This guide will concentrate on the 96-97 Passat, but a lot of the information here will pertain to the Jetta as well. The engine is rated for 90hp in stock form.

The Passat, 96-97

 The Passat is bigger than the Jetta, it seats four adults comfortably and there is plenty of leg room in the back, even for 6 foot plus passengers, and no, their legs will not be pushing the back of the driver's seat while driving. In fact, I am 6'4" tall and I have to have the driver's seat pulled up two notches from the back to reach the pedals! The back seats split and fold down giving you a lot of trunk space when you need it. I can take the front wheel off my ten speed bicycle and the rest will fit in the trunk with the back seats folded down. The whole bike will be inside the car with the trunk closed.
 The Passat has a softer ride than the Jetta, and is a much more refined car than the Jetta. The Passat is a great highway car (thats what Tdi's are for!) and will easily travel at 85 mph all day long. They have electric windows, front windows operate from the driver's door, rear window switches are on the dash, a little strange, but it works. The cars are only available with 5 speed manual transmissions. Please ignore the eBay auto listing feature that says that all Passat have automatic transmissions. From 2004 up they were only available with auto transmission, but 96-97 cars only have manuals!!! The car has a pollen filter for the cabin air. The air-conditioning is top notch in these cars; it is a manual system, no auto temp feature. But on a 100 degree day put the AC on and put the system into the recirc mode and the car will freeze you out. If you want the AC to blow cold on a very hot day the AC must be in the recirc mode or the air will be warmer. The controls are easy to operate and understand. All the Passats I have seen have a Premium AM/FM stereo system. The system is very nice and the head unit has a cassette deck in it. There was an optional trunk mounted cd player. They have cruise, tilt wheel, and power steering and power brakes. The only thing that is not power on these cars is the seats, the lumbar, tilt and forward and aft adjustment is manual.
The Passat has an 18 gallon fuel tank. You should get over 700 miles between fill ups!
 The TDI Passat was not as decked out as their GLX V-6 powered brothers. VW viewed these as basic transportation so there were few options to be had. The most common options that were available are:

1. Trunk mounted CD changer.
2. Leather interior. (kind of rare)
3. Sunroof (seems like most cars have them, but not all)
4. Alloy wheels. (factory alloys are kind of rare too)
5. Fog lights.
6. ABS (most VR-6/s had ABS, most Tdi.s did not)
7. Well, the TDI engine was an option too!

Passat quirks

 Now that you are familiar with the Passat Tdi I am going to go into some quirks and problem area found on these cars. The quirks about the car first. Some of these take a bit of getting used to.
  These cars have no glove box!! That's right, don't have one. There is storage on the seat base, in each front door (actually kind of roomy compartments on the doors) and a center console with a couple of storage areas. The drivers seats have pockets on the seat backs.
 Then there is the funky fold down cup holder mounted on the passengers side of the center console. It holds two good size cups, you have to lean a bit if you are driving to use it, but it works, and it is also easily broken and they are easy to change as long as you have between 50-75 bucks for a new one!
 I mentioned the two locations for the power windows, door and dash mounted.
 The air-conditioning control panel has one tiny bulb that lights up the whole AC control panel, well it tries to, but it is not very bright. You can figure out the controls in the dark, but it's almost not lit.
 If you have fog lights they are turned on by pulling the light switch out! You turn the knob to turn the headlights on and then pull the knob out for the fog lights.
Heat, for those of you up north, these engines are so efficient that they take a while to heat up. (In other words the engine does not produce much heat) In very cold climates you might want to look for one with seat heaters. When the cars are cold you should not drive over about 2500 rpm, once warm they love to be driven hard. In fact these cars have two sets of glow plugs, one set for warming the fuel up like any other glow plug you have ever heard about. The other set is in the coolant system, and on cold days that set of glow plugs warms up the coolant so that the cabin heat will work faster.
The engine has a cover and a belly pan. The engine cover is for deadening sound. The belly pan that seals off the engine compartment is there so that the engine warms up faster in cold weather. (Keeps the engine heat in the engine compartment)  Make sure you get them when looking at a car to buy. The belly pans are 360.00 new, and a lot of people leave them off because you they are a pan in the rear because you have to remove the belly pan to change the oil. So, some people leave them off. I don't recommend you do this in a cold climate.
 The most bizarre fuel door ever. It locks when the car locks and will only open when ALL the cabin doors are unlocked from the driver's seat! These cars did not have remote entry systems, but a lot of them do (either aftermarket or dealer installed) the standard system works like this. The car is locked, you get your key out put it in the drivers door lock, turn once the drivers door opens, twice unlocks all the doors, including the fuel door!!! If you turn the key once to unlock the driver's door the fuel door will NOT open. The other way to open it is to be inside the car and with the key on push the driver's door lock knob down, and then pull up on it from the driver's door. From inside the car all the doors will unlock, including the fuel door!

Passat trouble spots

 The most important thing about a Passat is the care the car has received. And the two most important things to know about any car you are going to purchase is when the timing belt for the engine was last changed, and what type of oil has the car been running on.
 Timing belt is due to be changed at 60,000 miles. If they are not changed when they are due you run the risk of the belt breaking and when that happens the pistons will contact the valves and that is NOT GOOD. The repairs for those failures can run into the thousands of dollars to repair. So, if you buy a car that has no known history on the timing belt, get it changed as soon as you buy the car. The timing belt should be changed along with the tensioner and the small rollers as well. The manual says that the belt needs to be changed, but the tensioner can fail as well and the result will be the same. So, at a minimum make sure you know when the tensioner and belt were changed. Aftermarket kits are 125.00 and the dealer will most likely charge you with 2.5 hours labor (guessing here), so you are most likely looking at close to 500.00 including parts at a dealership to change the belt. Not cheap, but don't do it and you will be out thousands. Special tools are required to do it yourself, it can be done and many do it, but it not a job for a beginner auto mechanic. You will also need a Vag-com to check the timing when you are done. (Vag-com is a computer scanning tool. It will read codes, check timing and all the onboard sensors.) If your cars belt chirps when the AC is running the harmonic balancer is most likely failing. There is an updated harmonic balancer available for them.  The updated one can be installed easily at belt time. They are like 65.00 at VW parts houses.
 The engine oil is a subject that can be debated for hours. So I will say this, do your research and make sure you are using the correct oil for your car. Which in these cars is a pure synthetic, 5w-40. Oils like Delvac 1, Amsoil European motor oil formula, and certain Mobil 1 oil is acceptable. The owners manual states an oil to use that is not correct! There was a service bulletin put out on these cars right after they were made to change to synthetic. Some people did not have trouble with the petroleum based oils, some did. The use of the wrong oil can lead to turbo failures, or the oil control rings on the pistons sticking into the ring grooves causing high oil consumptions. The Turbo is 650.00 at a good price and the engine ring job I am sure is in the thousands. Make sure you do your research and run the correct oil. When looking at a car for sale and the owner states he has had it changed every 3000 miles, well - DANGER!!!
 That most likely means the car has been to Jiffy lube all its life and trust me they don't have a clue as to what oil goes into a Tdi. The oil change interval is 10,000 miles on a TDI, no need to change it more often, just use the right stuff!!
These cars have trouble blowing the gage clusters during cold starts on very cold days with a weak battery. When this happens a lot of cars get new clusters installed and the mileage on them looks just like a new car, zero miles!! So, did you find a car with 58,000 miles original? ARE YOU SURE? Maybe a new cluster was installed. Might want to run a car fax report.
  Vacuum lines. The turbo and the computer use vacuum hoses to control everything. (Actually the car uses pressure to control things, not vacuum) They get brittle with age and will cause the computer to not get correct readings from the sensors and turbo and will give you problems. It is not expensive to change them, but it can lead to heartache if you don't. Everyone seems to recommend silicon vacuum tubing for replacement. (There is also a vacuum line inside the cars computer, change it too! It can give you fits even if it looks good, change it!)
These cars have an EGR system that can cause the intake manifolds to clog up with soot. You can get a lot of build up in the intake which chokes the air to the engine and the result will be low power. Some disconnect the egr, some turn the cycle times down with a Vag-com, and some just clean the manifold when it needs it. About a 3 hour job.
An old set of injector nozzles can give bad performance. I have seen problems with them at 90k miles and I have seen them go 200k miles. I say once you get 100k miles on them change them.
 VW uses a life time anti freeze, I would not recommend any other type be used, in other words if someone has used "green stuff" you should change it to the correct coolant (marked on the coolant reservoir) G12 is mostly what these cars would need, it is pink, G12+ is the replacement, it is bluish green (funky color) and is fully compatible with G12. If you have to change the fluid make sure all the green stuff is flushed out.
There was a service bulletin on the 97 models which puts a new intake manifold and computer in the car. This is called a "TV" recall at the dealership. It installs a new computer with a FA suffix on the computer model number.
Headlights, stock headlights have plastic lenses. They dull with age and then you can't see very well at night. A car with a set of E-code headlights is a plus. These are nice replacements that will allow you to see at night. Stock headlights are terrible!! And very dim, and dangerous! E-codes are around 350.00
Window regulators are weak in these cars. They will make a popping sound before they go bad. The regulators can be had for 75.00 bucks and they take a couple of hours to change.
The door handles are prone to failure. Sometimes you can fix them if you are handy; otherwise they are 100.00 or so a piece.
 If the car has alloy wheels and they are the factory type 195-60-14 type tires and wheels you will have a nice soft ride (or stock wheels) But, if the car has 16 inch aftermarket wheels with low profile tires your ride will stiffen up a lot. A lot of times the bigger wheels are put on these cars because someone installed bigger brakes on the front. Brake upgrades are nice as the Passat brakes are marginal; they work, but not well in the rain. So, if you think you are going to put the stock wheels back on one that has 16 inch aftermarket wheels you may be surprised that they won't fit because of the bigger brakes.
Ignition switches are known to fail, and is most likely a dealer item.

 Mods

There are tons of mods you can do to your Passat; you can make them your own personal ride. Some popular mods are:

Larger injector nozzles usually folks put European spec nozzles on, bumps HP to 110, very worthwhile mod
Chipped computer, gives more boost
Larger brakes
E code headlights
Leather interior from a GLX
Alloy wheels
Bilstein shocks to improve handling, and stiffen the ride
Short shifter
Retro fitting fog lights to cars without them
EGR delete

Conclusion

These are the highlights from what I can remember. I am sure that someone is going to email me and tell me about something I forgot. But the big question is can you live with one of these cars? First I only recommend these cars if you do a lot of highway driving. That's where they shine. My feelings are that these get better mileage on the highway than hybrids. They are bigger and heavier than most economy cars and get great mileage. Now for the bad part. Unless you drive these cars with great care and have them set up for getting the most MPG you can, you are most likely going to get something around 42 mpg summer, 44 mpg winter.  Which is what I get on my commutes to and from work.
 The eBay hype about the mileage these cars get is out of control in some ads. I have seen claims of 60 mpg. Not likely. These cars are robust cars and are well built, and do like to be driven hard. They are German built after all.  But please keep in mind that while the Tdi will go 300,000 miles with proper maintenance, the car body may not without a lot of repairs. After all the engine is the great part about these cars, but the body is still a car body and face it these are 10 year old cars now.
 If you are handy with tools and can work on your own car this maybe the car for you. If you depend on others for your car care you might find these to be expensive to own. For purely the cheapest total cost of ownership you might consider a Toyota Corolla.
 To sum it up these cars are a blast to drive, German engineering, great handling, and great mileage, they are not the small econoboxes. But, they do require special care and if taken care of will last many, many miles. I own two of them and would not dream of driving anything else except a new Tdi Jetta, which is out of my price range for now.
 Good luck on your Passat search!