With the recent influx of new TDI owners (no doubt driven by the oil market), I figured someone should make a comprehensive post where they can go to get information about their car and how to keep it running forever. A lot of the TDI owners know and love www.tdiclub.com , however, finding an answer to a basic question may take a while. My goal is to make it so this thread is a one-stop shop for TDI owners for all the essential info they need and want. Many of the following links will be from www.tdiclub.com , and some will be threads I or others have made up here. 
Q: How should I break in my shiny new TDI?
A: Drivbiwire on tdiclub.com has an excellent break-in procedure that many swear by. It's found
here.
Q: What oil do I need to use in my TDI? All this 505 talk confuses me.
A: 2004 and later - MUST use oils that meet VW505.01 or oils that use that as a start. Examples of this are Elf Excellium DID, Motul 8100 Specific, Castrol TXT 505.01 (this is the oil VW dealers use), and Pentosynth TS 505.01. Usually, said oils will have 505.01 in the name, or labeled clearly on the bottle. A false alarm was recently going around that Mobil1 T&S was 505.01 certified--that is NOT the case. Some initial confusion took place over at TDIclub when a member posted a potentially misleading document, that upon further examination and follow-up with an PD oil expert revealed that it is not certified and should NOT be used at all in PDs. I have the most current oil list and it appears that Mobil1 does have a product certified...however, it's only available in Europe. Props to tdi jerry for questioning that fact, he gets kudos...I'd have never questioned it at all but he sent me a PM questioning the validity of the claim.
The oil list I will post in a seperate thread, and will be stickied. 
For 1998-2003 TDIs, at least one of the following must be met (usually, any oil that meets one will meet the others)
A. VW505.00 (any oil that meets VW505.01 also meets this)
B. API spec CF4 or later (i.e. CG4, CH4, CI4 and CI4+ all work here).
C. Some ACEA spec which would be important in Europe.
Some examples of compliant oils would be Mobil1/Delvac1 Truck and SUV, Shell's RotellaT, Elf Excellium LDX, and Castrol's Syntec. All oils will have a viscosity of 5W40, and every major chain store carries at least one or two of these oils.
Q: Now that I know what oil to use, how do I go faster?
A: Well, my friend, there are many options, the most common being a software upgrade, commonly referred to as "chipping" or "flashing" the car's ECU. Vendors who have recieved high marks include Rocketchip and Upsolute . Many pre-2004 TDI owners upgrade their nozzles as well, and Kerma sells what many call the best.
Q: What's VW's stance regarding BioDiesel?
A: VW's "official" stance is blends up to 5% (B5) are acceptable. However, many owners both on here and on www.tdiclub.com run B20, and some even run B100. The best advice I can give if you run BioDiesel (especially if you bought your TDI used) is to keep a spare fuel filter in the car just in case. BioDiesel acts as a solvent (good for the motor and intake, bad for the fuel filter), and thus you may clog up a fuel filter or two in the beginning if you run B100.
Q: What additive should I use?
A: VW's "official" stance is that Stanadyne is the only PREFERRED additive, however, many of us also use PowerService to desired effect as well. It's basically your choice, both work equally well (8oz per 15 gallons is the ideal mixture) in the same dosages. Powerservice is commercially available at WalMart...so use what you can find.
Q: What is this CCV stuff I keep hearing about?
A: Well, this is where it gets tricky...every TDI responds differently to this modification. MANN makes something called the ProVent, which is a vent-style filter that when coupled with some hose, will make an excellent CCV system. It also costs $140, plus the hoses and clamps needed to make it work...far from a turn-key situation. However, many people choose to DIY all the way, and our own Eeyore has made an awesome setup for those on a budget (Aaron, I want a link to it
). This is one of those things where research will be your friend...what works for one may not work for another.
Q: I read somewhere that VAG-COM can adjust certain properties to make my TDI run better. Is this true?
A: Yes, it is, but only if you have a pre-2004 car. The PD motors do not support the tuning functions currently available through VAG-COM. If you have a 98-03 TDI, then you have a wealth of options available. You can adjust your EGR duty cycle (basically, you can make the EGR nearly inop-excellent for your intake) by changing the EGR value from 32768 to 33768 in the Adaptation screen. You can also adjust your IQ (injection quantity-how much fuel you give the motor) as well. Any number between 1-4 is good stuff. TooRoundTDI and I figured out that on his stock 99 ALH with 74k that 2.6 was best for him...your results may vary. For additional information on this subject, please visit www.ross-tech.com .
Q: Clogged Intakes? Eep!
A: My thoughts exactly. However, there is something you can do to help the situation out. Use the best diesel you can find (just because it says premium does not make it better; ask to see a spec sheet), run a good additive, and above all else, exercise your TDI.
They like to stretch frequently, so a couple times a tank, run it to 4k rpm (after following the breakin procedures of course if it's new), and just go through the first few gears. Also, running blends of biodiesel helps tremendously as well. B100 (100% Bio) produces 80% less soot than regular old diesel, which means 80% less soot enters your intake. Running regular old diesel from Joe's Gas with no additive and driving it like Grandma on her way to church will clog an intake by 40,000 miles. Running an additive (or better yet, a Biodiesel blend) will extend that interval even farther out. Running a CCV system as described earlier, even with the cheap rotgut, will keep clogging down as well. The combination of oil and soot leads to a clogged intake, so I say an ounce of prevention (however you decide to go about it), is worth a pound of cure (in this case, saving $700 or so to clean the intake and turbo). See above for CCV system info.
Q The glow plug light is flashing, what gives?
A Believe it or not, most likely problem is with the brake lights. Either the lights are burned out, or the brake light switch is bad. In a car with automatic transmission, it will be "stuck" in park as well.
Q The CEL light came on, and I got it scanned at AutoZone. They said that the code was for the glow plugs. Now what?
A Remove the harness, and use a multimeter set on the lowest setting. Check the resistance between the tip of the glow plug and ground. The acceptible range is .5 to 1.5 ohm. You are looking for one or more glow plugs that are different from the rest. If you find a bad glow plug, in 98 to 2000 cars, replace all four. In 2001 and later replace in pairs, 1-2 and 3-4. Always best to replace all 4 regardless.
Note: The harness itself can sometimes go bad, and needs to be replaced.
Thanks go out to Dorado, Eeyore, maxforce, hannaco (for the glow plug info), scooperhsd (for the oil clarification), and all the guys at tdiclub.com who have helped me, and thus enabled me to help others. I'd also like to thank the owner of the Dodge pickup who hit my Jetta and totalled it, looking back, it was the best thing to happen to me...I met a whole new group of people who care about one another, and would give their last dollar (or liter of 505.01 oil
) if need be to another member.
This is a work in progress...PM me if you have stuff to add and I'll add it.
Q: How should I break in my shiny new TDI?
A: Drivbiwire on tdiclub.com has an excellent break-in procedure that many swear by. It's found
here.
Q: What oil do I need to use in my TDI? All this 505 talk confuses me.
A: 2004 and later - MUST use oils that meet VW505.01 or oils that use that as a start. Examples of this are Elf Excellium DID, Motul 8100 Specific, Castrol TXT 505.01 (this is the oil VW dealers use), and Pentosynth TS 505.01. Usually, said oils will have 505.01 in the name, or labeled clearly on the bottle. A false alarm was recently going around that Mobil1 T&S was 505.01 certified--that is NOT the case. Some initial confusion took place over at TDIclub when a member posted a potentially misleading document, that upon further examination and follow-up with an PD oil expert revealed that it is not certified and should NOT be used at all in PDs. I have the most current oil list and it appears that Mobil1 does have a product certified...however, it's only available in Europe. Props to tdi jerry for questioning that fact, he gets kudos...I'd have never questioned it at all but he sent me a PM questioning the validity of the claim.
For 1998-2003 TDIs, at least one of the following must be met (usually, any oil that meets one will meet the others)
A. VW505.00 (any oil that meets VW505.01 also meets this)
B. API spec CF4 or later (i.e. CG4, CH4, CI4 and CI4+ all work here).
C. Some ACEA spec which would be important in Europe.
Some examples of compliant oils would be Mobil1/Delvac1 Truck and SUV, Shell's RotellaT, Elf Excellium LDX, and Castrol's Syntec. All oils will have a viscosity of 5W40, and every major chain store carries at least one or two of these oils.
Q: Now that I know what oil to use, how do I go faster?
A: Well, my friend, there are many options, the most common being a software upgrade, commonly referred to as "chipping" or "flashing" the car's ECU. Vendors who have recieved high marks include Rocketchip and Upsolute . Many pre-2004 TDI owners upgrade their nozzles as well, and Kerma sells what many call the best.
Q: What's VW's stance regarding BioDiesel?
A: VW's "official" stance is blends up to 5% (B5) are acceptable. However, many owners both on here and on www.tdiclub.com run B20, and some even run B100. The best advice I can give if you run BioDiesel (especially if you bought your TDI used) is to keep a spare fuel filter in the car just in case. BioDiesel acts as a solvent (good for the motor and intake, bad for the fuel filter), and thus you may clog up a fuel filter or two in the beginning if you run B100.
Q: What additive should I use?
A: VW's "official" stance is that Stanadyne is the only PREFERRED additive, however, many of us also use PowerService to desired effect as well. It's basically your choice, both work equally well (8oz per 15 gallons is the ideal mixture) in the same dosages. Powerservice is commercially available at WalMart...so use what you can find.
Q: What is this CCV stuff I keep hearing about?
A: Well, this is where it gets tricky...every TDI responds differently to this modification. MANN makes something called the ProVent, which is a vent-style filter that when coupled with some hose, will make an excellent CCV system. It also costs $140, plus the hoses and clamps needed to make it work...far from a turn-key situation. However, many people choose to DIY all the way, and our own Eeyore has made an awesome setup for those on a budget (Aaron, I want a link to it
Q: I read somewhere that VAG-COM can adjust certain properties to make my TDI run better. Is this true?
A: Yes, it is, but only if you have a pre-2004 car. The PD motors do not support the tuning functions currently available through VAG-COM. If you have a 98-03 TDI, then you have a wealth of options available. You can adjust your EGR duty cycle (basically, you can make the EGR nearly inop-excellent for your intake) by changing the EGR value from 32768 to 33768 in the Adaptation screen. You can also adjust your IQ (injection quantity-how much fuel you give the motor) as well. Any number between 1-4 is good stuff. TooRoundTDI and I figured out that on his stock 99 ALH with 74k that 2.6 was best for him...your results may vary. For additional information on this subject, please visit www.ross-tech.com .
Q: Clogged Intakes? Eep!
A: My thoughts exactly. However, there is something you can do to help the situation out. Use the best diesel you can find (just because it says premium does not make it better; ask to see a spec sheet), run a good additive, and above all else, exercise your TDI.
Q The glow plug light is flashing, what gives?
A Believe it or not, most likely problem is with the brake lights. Either the lights are burned out, or the brake light switch is bad. In a car with automatic transmission, it will be "stuck" in park as well.
Q The CEL light came on, and I got it scanned at AutoZone. They said that the code was for the glow plugs. Now what?
A Remove the harness, and use a multimeter set on the lowest setting. Check the resistance between the tip of the glow plug and ground. The acceptible range is .5 to 1.5 ohm. You are looking for one or more glow plugs that are different from the rest. If you find a bad glow plug, in 98 to 2000 cars, replace all four. In 2001 and later replace in pairs, 1-2 and 3-4. Always best to replace all 4 regardless.
Note: The harness itself can sometimes go bad, and needs to be replaced.
Thanks go out to Dorado, Eeyore, maxforce, hannaco (for the glow plug info), scooperhsd (for the oil clarification), and all the guys at tdiclub.com who have helped me, and thus enabled me to help others. I'd also like to thank the owner of the Dodge pickup who hit my Jetta and totalled it, looking back, it was the best thing to happen to me...I met a whole new group of people who care about one another, and would give their last dollar (or liter of 505.01 oil
This is a work in progress...PM me if you have stuff to add and I'll add it.