2) Use any oil that has a VW 507.00 specification (low-ash properties for protecting the diesel particulate filter (DPF)). These oils are synthetic by nature of the 507.00 specification and at this time they only come in 5W30 weight. Don't use any other oils. You will only find such oils at VW dealers and specialty Euro shops. You can also find them online at places such as ecstuning.com and idparts.com. The oil from the dealer is generally Castrol SLX Professional and comes in a gold bottle with a red cap. Always verify that's it's VW 507.00 rated. I purchase Pentosin Super Performance III 507.00 from ecstuning.com in 5L jugs.
http://www.ecstuning.com/Volkswagen-Jetta_V--TDI/Maintenance/Engine/ES1884221/
You can also get Mobil 1 ESP 507.00 at Pep Boys in 1L containers. My 2009 Jetta takes exactly 4 liters, but you're going to have to purchase 5L the first time, fill it with 4L, run the engine for a few minutes, and check the level to see how much, if any, of the 5th liter you have to add. In my case, I nailed the top line of the dipstick with 4L and didn't even need to crack open the 5th liter. 5L is overfilled and can damage things. Most people use 4.0-4.3L, some have used 4.5L.
You may be able to find a NAPA that carries Lubro Moly TopTec 4200, another 507.00 oil, in 5L bottles. My local one said they can order it and have it shipped to the store in their next batch, but they never called me when it arrived, so your mileage may vary. Price is cheaper at IDParts/ECS Tuning (around $55 at NAPA, $40-something at IDParts/ECS Tuning).
Also, please do not get your oil changed at Jiffy Lube or Walmart unless you watch them do it, explain the 4L vs 5L thing that I just explained, and provide the oil yourself. Many parts counter guys will say all synthetics are the same, and this does not apply to your expensive emissions system, which depends on VW 507.00 oil. If you absolutely have to use an oil that isn't VW 507.00 certified, you can (void your warranty and) use Mercedes-Benz 229.51 (aka MB 229.51) certified oils. A good oil that meets that is Mobil 1 ESP Formula M, which is 4 cents more expensive than Mobil 1 ESP and is located right next to Mobil 1 ESP at Pep Boys (so I just use Mobil 1 ESP).
In a pinch - and I mean, it's low and you can't possibly get to a VW dealer or Pep Boys in the next month because you're on the top of a mountain that is thousands of miles away from a dealer - you can use a high quality Diesel engine oil (Rotella T9 for example) to top off only... But as soon as you can, drain and refill with the right oil.
