Black diesel!

Hi,
"Today, I replaced the fuel filter on my Altea 2.0 TDI BMM. I believe this was the first fuel filter replacement. I noticed the black discoloration of the diesel fuel. The engine is running completely normally. Mileage: 63,000 km. What could be the cause of the black discoloration? Could it be engine oil?" If so, where from?

LG
Alex.

Hello,

Theoretically, in a boxer engine, there could be a connection between engine oil and fuel in the cylinder head, for example, due to a crack.

In practice, it sometimes happens that used motor oil is disposed of profitably at gas stations. I probably experienced this a few years ago in Nuremberg, when all the transparent hoses in the engine compartment suddenly turned black.

What does the engine oil look like? Is the level decreasing, increasing, or is it "diluted"?

Best regards, Rainer.

No engine oil consumption or diesel smell (coming from the valve cover) could be detected.

LG
Alex.

I also observed this last week. However, I was told beforehand that contaminated fuel was being used. The slurry will naturally flow outwards when the filter is removed.

Quote:

theoretically, in a BMM engine, there could be a connection between engine oil and fuel in the cylinder head (ZH), for example, due to a crack.

Shouldn't it eventually suck in air, and conversely, could diesel fuel then get into the engine oil?

"Adulterated diesel fuel! I've experienced that myself, on several occasions." It is advisable to hold the nozzle in a way that allows you to visually assess the fuel being dispensed when refueling at gas stations that you do not trust.

Important: Immediately raise the alarm at the gas station and involve decision-makers. The more customers who cause a disturbance, the better. You shouldn't have to pay a lot of money to be sold this garbage!

Hello,

Quote:

Shouldn't it eventually draw in air, and as a consequence, could diesel fuel potentially leak into the engine oil?

Possibly yes, for example, a crack could exist from the engine oil (pressure oil) to the fuel return line. That's why I'm asking about the fill levels.

Best regards, Rainer.

I've replaced the filter element again. It looks much better than before. The first filter is on the left, and the second filter is on the right. I will perform another check after 2-3 tankfuls of fuel.

Since the engine levels haven't changed, it seems (fortunately) that it was probably just adulterated fuel .

LG
Alex.

Hi,

To me, it doesn't necessarily look like adulterated diesel, but rather like degradation products from the biodiesel blend. A precise statement can only be made after analyzing the residues.

It's no surprise that the quality of diesel fuel has deteriorated significantly. At our on-site fuel station, the color of the diesel from the same supplier varies between black, milky-white, and pale yellow, depending on the batch.

A tanker truck driver told me that they rarely refuel at the nearest refinery, but always go where it's cheapest (e.g., a port for diesel from Eastern Europe).

"I always do a visual check to see what color the fuel dispensed from the gas station pump is. I only insert the nozzle a short way and let it run slowly. If the fuel is black, red, or pink, I immediately stop and complain to the gas station staff. In addition, I report it to the authorities (initially as a criminal complaint for "fraud"). The addition of alto-octane additives, as well as excessive amounts of heating oil that can be chemically detected, are clearly fraudulent." I will not pay for someone to mix their used oil into my expensive fuel, and I will not participate in any tax evasion schemes related to the heating oil additive.

While I cannot scientifically prove this, I claim that various problems with injectors and DPFs are due to fuel that is outside of the normal specifications. Whether foreign substances are accidentally or intentionally added, or whether the water content is simply too high due to the hygroscopic properties of biodiesel.

It is unlikely that anyone would regularly take samples at the fuel pump under notarial supervision, seal them, and send them to a laboratory for analysis .

Primarily, a lot can be added to diesel fuel that wouldn't be immediately noticeable either during refueling or during subsequent use. The engines start as usual, run normally, and any damage caused by the adulteration typically doesn't become apparent until much later. This makes it impossible to establish a direct link between the damages that occur and the adulterated fuel, and to identify a specific source for that adulterated fuel.

But take heart, it's just as easy to siphon gasoline. In addition to cleaning and dissolving agents, other chemical residues are also sold. Gasoline with a smell reminiscent of brush cleaner already caused excitement among my friends. Among motorcycle riders, there were carburetors that were leaking, but otherwise the bikes ran unaffected. A 2.0 Vectra A only started with the accelerator pedal, but ran normally when warmed up, and occasionally exhibited occasional after-running after the ignition was switched off. All vehicles that were refueled at the same gas station had completely black spark plugs and a very distinctive exhaust smell (comparable to that of a gasoline engine without a catalytic converter shortly after a cold start).

In the 2004 case, according to a newspaper report, large quantities of used industrial cleaning agent were roughly filtered and disposed of through a gasoline distributor, which then supplied several gas stations. However, virtually nothing happened to the car at the time; allegedly, there was no engine damage, and even if there was, proving direct causation would have been a complex and lengthy process.

My thoughts are going in the following direction:

DPF engines use low-ash engine oils to prevent ash from the engine oil from entering the DPF. When old engine oil (which is usually not low-ash), hydraulic oil, or even worse, transmission oil, is added to diesel fuel, the ash content in the fuel increases significantly.
Of course, the DPFs (Diesel Particulate Filters) of the vehicles fueled with this product will fail much sooner due to clogging from ash.

The customer pays, because how can he prove that he ever filled up with substandard diesel at gas station x?

Exactly. The engines usually start running first, and for that reason, the problem often doesn't become noticeable until much later, or not at all.

While it's an older topic, I don't think your assumption about the diesel being adulterated is entirely correct.
Here in the northern regions (Denmark), the 2.0 TDI engines are quite known for their tandem pumps leaking and drawing oil from the cylinder head. I know, it sounds unlikely, as there's a pump in the tank and the line from the tank should be under pressure. However, the oil is being sucked in. This mixture then goes back into the tank through the return line and from there into the filter. The first signs of this are oil in the diesel filter. Later, you'll experience poor cold starts and power loss during acceleration. This problem is absolutely not an isolated case, and you read about it quite frequently. The mileage of the engines varies greatly, ranging from a few tens of thousands to well over 200,000 kilometers.

"In this VW forum, a member once took the trouble to investigate this issue (it's in Danish, but the photos are quite self-explanatory, especially the last one)."
I am sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.
It's clear that the pump shaft is wearing down, which then damages the oil seal towards the camshaft.

The repair at the dealership includes, among other things, replacing the fuel tank, as it is considered beyond cleaning. Including a new tandem pump, tank, and flushing of all lines, the total cost is between €1,800 and €2,200.
The strange thing is that as someone who tinkers with things, you can definitely verschandeln the tank (simply with some rags and patience), and then it will also work with a new tandem pump and two filter changes alone.

/Jan

Jan03 wrote:

It's an older topic, but I don't think your assumption about the diesel being adulterated is entirely correct.

Hello Jan,

How do you explain...?

Quote:

I have now replaced the filter element again. It looks much better than before. The first filter is on the left, and the second filter is on the right. I will perform another check after 2-3 tankfuls of fuel. Since the engine levels haven't changed, it seems (fortunately) that it was probably just tampered-with fuel

.
His tandem pump is unlikely to fix itself simply by changing the fuel filter. The tandem pump could, of course, also fail, but in his case, it is probably not.

Best regards, Rainer.