Baja

I changed the oil in our Jetta TDI, and within 50 miles is was very black, like I hadn't changed it at all . What would cause this? Any ideas? I guess I will have to get a oil test, any companies other than Blackstone? Thanks in advance.

Tiny

Soot from the diesel. No worries, keep it topped off and you will be fine.

G1625S

Yup, it's the soot. That's why it's important to purchace an oil that's rated for diesel engines. Those oils have an additive that helps suspend the soot so that it cannot contact things like main bearings.

Geico266

While I agree diesel motor oil will turn black,50 miles might be a sign something is wrong, but you did not mention how many miles are on the car or how old it is. Does it smoke when driving?

CoastalDav

My Cummins does not turn dark until 5000 miles and you can still see the dipstick through the oil. I use Rotella which is light in color to start with. Truck has 157K on it. Other oils start off dark and take less time to turn.

My previous diesel vehicles all turned black in the first 500 miles. 7.3, 6.2 and 5.7. They did not control combustion in the cyclinder like the Cummins. Most of that soot is put there when the engine is cold.

Thats interesting about the Jetta. I thought their engines were tight.

Dave

Baja

Mileage is 55,000. I used Rotella. Is soot a bad thing? Can it be controlled, or filtered out using a better filter? The only time smoke occurs is when I floor it on take-off, other than that, the car runs perfectly.

CoastalDav

I know very little to nothing about the Jetta Diesel so I can't get technical about what it could be or whats normal.

You may consider taking an oil sample toward the end of the oil change period or at the oil change and send it in for analysis. The next thing you may consider is checking compression to see if its OK and then the injection pump to see if its overfueling. There is only two things that make a Diesel smoke, to much fuel or not enough air. That combination will make lots of soot.

All of the Diesels I had that ran with a lot of soot, never had any problems. When I got my first Cummins in 96 I could not believe how long it would go without turning black. Now to me anything that runs black in the bottom most likely has compression problems. Not wear problems, just does not hold the compression like the cummins. Those other engines relied on the engine heat to expand the rings and hold compression. I think the cummins runs one additional compression ring to help.

Dave

BigBlue

Don't forget that even though you may drain the oil out of the pan that there is still some old oil floating in the engine and that will turn it black also.

v8440

The CR cummins, particularly the 04.5's and later with the 3rd injection event, are well known to have their oil get pitch black in no time. Fifty miles is totally common from what I've heard several times. My own experience with 3 of them bears this out. Don't worry, in other words.

Raspy

You cannot stop the formation of soot in a diesel, and the soot in the oil is what went past the rings as blowby. No big deal, won't hurt a thing. My old 6.9 dirtied the oil in no time and my new Passat does it quicker than I expected, probably in about a thousand miles. I change the oil in my Cummins every ten thousand miles and the oil is only brown by then. Wow, the Cummins is really tight on compression! Just one more thing they do right.

John

NoSparkplugs

I was flipping through my Diesel Power magazine and I saw an ad for a product called the "Soot Sucker". I guess its an external oil filter that removes the soot from the oil and it keeps the oil that golden honey color. From the ad I gathered that it was a Powerstroke specific kind of thing. But if soot isn't to be worried about I don't see the point of having the system .

IA_James

Sounds like a product for the "extended drain" crowd, probably no much use for anybody else.

Guardrail

It's normal. You will never get all the oil out of an engine when you change unless you let it drain overnight.

My Mack has a high pressure Spinner oil filter that filters out very small particles at very high pressure. The oil still turns black after I first start it up to check the oil filters and such for leaks. I don't even have to drive it anywhere.