I was reading the owner's manual and it talked about checking the oil for fuel dilution. The first time I changed my oil was at 3k and again at 6k, oil was very thin and black(truck now has 7500 miles). Could this be from the engine not being fully broken in? Or bad diesel? Something else? It's my first diesel and I love the mileage so far. Best tank was 18.6 running 75-78 all highway with only 2500 miles on the odometer. Okay for a first post?

Matt aka Thenewguy

 

fuel dilution is caused by a leaking injector. It leaks diesel fuel into the crank case there for diluting the oil with diesel fuel. For the most part you can smell the oil on the dip stick to make sure is does not smell like diesel fuel. If it does you may have a injector gone bad. The oil being a black color is very normal for a cummins. Mine turns black after a oil change in about 5 miles.

 

So the only way to tell if the oil is diluted is to smell the oil? I also heard that taking shorter trips is bad for diesels. I'm guessing that the rings don't get hot enough to expand and fuel can get pushed down into the crankcase.

 

short trips does 2 bad things. 1st, not warm enough, doesnt burn fuel completely and creates deposits. 2nd, doesnt heat up the oil enough to remove moisture, so water stays in the oil and turns acidic. which eats components.

fuel dilution is measured by taking oil samples and getting them analyzed.

 

If you were to have a serious fuel dilution problem [faulty injector] your oil level is probably going to rise pretty quickly. Imagine if you poured a quart of diesel fuel into your oil sump what it would do to your oil level. If your dipstick oil level remains constant, or less, your probably not getting any significant amounts of fuel dilution. Fuel blowby should be minimal with normal driving habits and constant oil levels in well maintained young engine. Soot loading - yes [black oil] - but a good oil will keep it in suspension until you drain it. Remember these engines have 12 quarts of oil, so a routine amout of fuel blowby can be tolerated.

Anytime you can take a long drive, tow or climb long hills/mountains it's good for the engine since it gets it up to temp and puts a load on it that helps burn off deposits. My truck seems to really purr after a tow or long road trip.Long idling is the big no-no! I am a beliver in a good fuel additive to help keep injectors and fuel system clean which aids the combustion process.

You can always do an oil analysis and establish a baseline for later analysis comparisons if the fuel dilution gremlin should keep you awake at night. Otherwise, I would not worry about it as long as your oil level is steady, you are not doing excessive idleing and you can really exercise the beast every now and then.

 

what is considered long ideling?

 

Thanks for the help. I read somewhere else on this site that about some kind of mileage flash. It was instructions for a dodge tech to perform. It said to check % of idle time. Anything over 20% is considered excessive. Hope that helps.

 

Anytime you really don't have to! Thats my guideline.

The 20% accumulated idle time seems to be the crossover point. But why idle if you don't have to? In addition to risking too cool combustion temps it wastes fuel [decreases mpg] and contributes to adding pollutants into the air. Obviously you are forced to at red lights, stop-n-go traffic, etc. and that is what contributes to a part of that 20% measurement. My pet peeve is when my wife drives the truck and is on her dang cell phone pulls into the driveway and leaves the engine running while she tries to finish the conversation. Honey, your cell phone does not need the engine running in order to work! I think I finally got her broken of that habit.

However with that said, I do let my truck idle to cool down the turbo if for instance I have just pulled off an Interstate hi-way for a fuel stop, etc. during a long trip or towing a load. You want to allow the oil to wick or transfer the heat out of the turbo bearings/housing by allowing it to cycle through for a couple minutes, plus as an added benefit, it helps cool the automatic's transmission fluid when idling in Neutral. This is where it helps to have gauges to know when it's necessary and for how long.

 

I tow for my own company and when I fuel up I let my truck run the whole time the only time I really lt it idle is in the winter when we get a cold snap and it's 20 below I will let it idle while I go into the grocery store for a few things. when the wind is blowing here at -15 or -20 my 98 12 valve would start hard even after sitting for 20 minutes. it would get cold very fast. oh one more thing how do the newer crd's like the cold? I was able to (but didn't like to) start my 12er in -20 weather unplugged.

 

I'm in agreement with pretty much everything that has been said so far.

My oil is black, and that's with a double bypass filtering system.

I also recommend getting an oil analysis done every 6000-7000 miles just to check out how the internals are doing. Kinda like getting a blood test, but for your truck.
My analysis have all come back very good, even with the black as coal oil...

 

Where would I take a sample of oil to get it analyzed? How much oil? Cost?

 

You could wait until you change the oil, then send a sample in.
You could get one of those tubes that goes down in the dipstick tube and draw out a couple ounces from there also.
I use Blackstone laboratories. They'll send you a free sample kit that includes the bottle for the oil and the container for the shipping. I think it costs about $15 for an analysis. I think I pre-purchased like 6 of them for a cheaper cost overall.
There are other companies out there. Others will chime in I'm sure...

 

Ok, I had some serious fuel & oil dilution today. I hopped in my truck cranked it up glanced at the miles to zero gage and took off home from work. When I got in the truck the gage read 347 miles to zero... I got off the interstate about 10 miles down the road... Hit the first stop light. Glanced back up and it reads 225 miles to zero. Hmm, next light I started to smell fuel. a few miles down the road I still smelled fuel pretty bad. A few miles later it seemed to be running rough at idle. So I pulled over.. Poped the hood and saw smoke. I went another 5 miles to the dealership... Pulled in... They hopped right on it. They put it on the lift. The whole undercarriage of my truck was covered in oil & fuel. Diesel was blowing right out of the crank case overflow. The service guy seems to think it's a bad injector... Ya think? I'm just wondering if the engine has been damaged or the bearings hurt from this. It's an 05.
any help?

 

I've been having nightmares about this same situation lately.

I hope you didn't ruin the engine... it can't be good for the bearings and turbo having all that diesel in there...

Keep us posted...

 

Yeah Offshore80 keep us posted on the diagnosis. Hearing of more and more of these late model 05/06 injectors going South at such low miles is giving me the WILLLIES! Fill out your signature so we know what you have on your truck.

That's very interesting and insightful that you had your overhead on the DTE setting and noticed the quick drop in DTE readings. Maybe we should rename this from DTE to "DIF"...Diesel In Fuel indicator! If it's that quick to account for the fuel injection rate it is a good indicator that something is a-miss when it drops the DTE so quickly. That or you really have your foot into it or someone just pulled up alonside and is siphoning out your fuel Roadwarrior style! Anyway thanks for the tip...my DTE reading is going to mean a lot more to me from now on.