What are the details of the vehicle?
Do you have VCDS?
Fuel pump is external, so how could it leak into your oil?
Injector seals would cause the combustion chamber to "vent" to the outside, so you'd be getting signs of black death.... once again, wouldn't leak into your oil.
Sounds like you're grasping at theories but don't really understand what you're saying!

 

I am grasping at theories, honestly. Hence the post and me stating "I'm just guessing at this point so I'm hoping someone with more knowledge can chime in". I figured I made it quite clear that I'm lacking knowledge in this area. I thought this is a place where someone could post to learn and gain knowledge from others? No?

 

Which part of what I said didn't provide you with knowledge?
Did you miss the parts where I explained to you why none of what you suggested could be a thing?

 

Where in my comment did I say you didn't provide any knowledge? Did you miss the part where I never said that?

 

So if you didn't say or imply that, why did you ask if this is a place where you can gain knowledge from?
Did you answer my questions or are you more interested in linguistics?

 

I asked that in response to your completely irrelevant "sounds like you're grasping at theories but don't really understand what you're saying!" comment. I made it quite clear in my original post that I was "guessing" and looking for more information so I'm genuinely confused why you added that completely useless last sentence onto your post. It provides zero intelligence to the conversation, especially when it's already been clearly communicated. But hey, maybe you're just a person who thinks "grasping at theories" and lack of understanding on a subject doesn't belong in online help forums 🤷

- Vehicle is a 2015 TDI. 200,000km. Oil changes every 10k (km) since new. I recently purchased the vehicle. No CEL's. Starts and runs normal. No symptoms besides oil being very clear and light colored (not black at all) even after driving 300+km, viscosity feels slightly diluted, exhaust has a weird chemical-like smell. Oil currently being used is LM TopTech 5W-30. Paper towel test showed signs of fuel in the oil I collected from the previous change.

- I do have access to VCDS if I need it (have a friend). I just don't know what to look for if I hook it up.

Mostly wondering if there are typical places to start looking in attempt to identify where the fuel is getting into the oil.

 

Failed DPF regenerations can deposit diesel fuel in the sump - they fail if you do lots of short journeys and the regeneration doesn't get chance to complete.

 

Interesting. This is helpful. So I recently purchased the vehicle, and I don't know if the previous owner took a bunch of short trips or not. However, I personally take longer highway trips (45-60min one way) to work. So regens would definitely have time to complete.

If what you described is indeed the issue, would this issue clear up on its own with regular regens and highway driving? Or has damage already been done and fuel will continue to enter the oil?

 

A bad dpf or leaking injector seals can leak diesel into oil. Short trips can also do this. Lots of idling can dilute oil as well.

If you have fuel in oil that's a very bad sign.

 

A bad dpf or leaking injector seals can leak diesel into oil.

Nope

 

Diesel fuel is just a light oil, there is essentially no reliable way to identify engine oil fuel dilution at home without a professional chemical oil analysis. Send your oil to Blackstone and report back.

I find it impossible that your engine oil is clear- and wonder if you're even actually checking your engine oil. You could fill and drain the crankcase to the top and drain/flush with fresh diesel fuel or kerosene 10x, and it would still instantly be pitch black seconds after starting the engine - it takes very little soot to make engine oil black. Diesel fuel will get filled with soot and turn black just like proper oil does. Please send a photo of your clear engine oil on the dipstick.

Second, if you were getting fuel dilution and didn't have massive leaks/oil burning, you would see increasing oil levels on the dipstick.

Diesel oil dilution is a potential problem on common rail TDIs due to regens, but none of the other stuff mentioned can do it- you cannot have injector or fuel pump problems that cause it without running issues or posting codes.

 

I happen to own an identical 2015 TDI to the one that's having these "issues", so I've done quite a bit of oil changing and checking in the past. I do whatever maintenance I can myself. A dipstick is the first thing I add to these vehicles when I buy them. And I can assure you that my oil is still very light and clear even after 400km of driving. I've never seen anything like it which is what lead me to dig into this in the first place.

I can send a photo of the dipstick later today, but I have attached a photo of the paper towel test. The oil on the left is my healthy 2015 TDI with 400km driven. The oil on the right is the 2015 TDI I am posting about after also driving 400km. As you can see, the oil is extremely light and has that "halo-like" aesthetic to it. And that's how light it is on pure white paper towel. You can probably imagine how clear it is on my dipstick.

 

Anyone know if it is possible to identify if regens are failing with VCDS, and exactly how often?

 

Yes you can see when the last one was and the duration and other statistics surrounding it

 

Maybe you have a gasser with a TDI badge on it

 

I wish that were the case at this point.

 

My oil is instantly black after an oil change. Can’t see how yours isn’t. Weird.

 

Yep. Looks like this even after driving 400km. So so strange.