Dealer oil change

[shadow gray 2020 hd]

Had my oil changed at the nearest dealer about 500 miles ago, maybe 2 weeks ago on my 2020 duramax.  The second oil change, and the truck only has a little over 10,500 miles on it.  I checked my oil today and it is black!  Level is full, but it is black and looks old.  Won't be able to get the truck to the dealer until next week. 

 

Am I wrong in thinking the oil could not be the way, unless they didn't actually change it?  I did not check the oil at the dealership before I pulled off the lot, but will from here on.

[Grumpy Bear]

Happens to ALL diesel motors. Combustion soot colors the oil. It's fine. First time you noticed this in 10K miles? Yikes! Check you level more often. 

[Z45]

Oil Myth: The color of the oil indicates when it’s time for an oil change

It’s common to assume that black motor oil has worn out or become too saturated with contaminants to protect your engine and requires changing. Not necessarily.

The only surefire way to determine if the oil has reached the end of its service life is to perform oil analysis. Chemically analyzing an oil sample reveals the condition of the oil, the presence of contaminants, fuel dilution and so on.

Absent oil analysis, it’s best to follow the oil-change recommendation given in your vehicle owner’s manual or by the motor oil manufacturer.

It’s best to trust the data, not your eye, in this case. Otherwise, changing the oil could amount to throwing away good oil.

• Heat cycles naturally darken motor oil
• Soot causes oil to turn black

[Black02Silverado]

Black oil is what happens to diesels.  My 2014 Cruze diesel is black pretty much after I change it and drive it off the ramps.  Not really pitch black but after a few miles it gets to be the normal diesel black oil. 

[shadow gray 2020 hd]

15 hours ago, Grumpy Bear said:

Happens to ALL diesel motors. Combustion soot colors the oil. It's fine. First time you noticed this in 10K miles? Yikes! Check you level more often. 

I have checked it at intervals, after the first oil change, around 400 miles after that change it was not black like this.  I am talking about pitch black.  A thousand or more miles after a change, yeah I see it being black, and would not think anything about it.    

[Z45]

Soot causes oil to turn black

While heat cycles cause oil to darken, soot causes oil to turn black. Most people associate soot with diesel engines, but gasoline engines can produce soot as well, particularly modern gasoline-direct-injection engines.

Soot is a byproduct of incomplete combustion. Since soot particles are less than one micron in size, they typically don’t cause engine wear. For comparison, a human hair is roughly 70 microns in diameter.

If soot particles agglomerate into larger wear-causing contaminants, the oil filter will catch them. Sometimes people who use bypass filtration systems, which can filter contaminants down to two microns, express surprise that the motor oil is still black. Soot, however, can still elude filtration down to two microns. Any finer filtration and the filter could catch dissolved additives in the motor oil.

[Grumpy Bear]

1 hour ago, shadow gray 2020 hd said:

I have checked it at intervals, after the first oil change, around 400 miles after that change it was not black like this.  I am talking about pitch black.  A thousand or more miles after a change, yeah I see it being black, and would not think anything about it.    

 

Then it is dong better than many. Be happy...don't worrry. 

[Supreme Pizza]

On 12/16/2021 at 2:24 PM, Grumpy Bear said:

Happens to ALL diesel motors. Combustion soot colors the oil. It's fine. First time you noticed this in 10K miles? Yikes! Check you level more often. 

 

 

Haha, Ya, you should check your oil more often. I check it every time I fill the fuel, on every rig I own.

[redwngr]

On 12/18/2021 at 3:13 AM, Supreme Pizza said:

 

 

Haha, Ya, you should check your oil more often. I check it every time I fill the fuel, on every rig I own.

Hopefully they get a 'cold' check once in a while too. 

 

 

[KARNUT]

I thought by now most vehicles had a trigger check oil light when they reach a qt low or 2. 

[newdude]

On 12/16/2021 at 4:53 PM, shadow gray 2020 hd said:

Had my oil changed at the nearest dealer about 500 miles ago, maybe 2 weeks ago on my 2020 duramax.  The second oil change, and the truck only has a little over 10,500 miles on it.  I checked my oil today and it is black!  Level is full, but it is black and looks old.  Won't be able to get the truck to the dealer until next week. 

 

Am I wrong in thinking the oil could not be the way, unless they didn't actually change it?  I did not check the oil at the dealership before I pulled off the lot, but will from here on.

 

 

Normal of all diesels. 

[Supreme Pizza]

4 hours ago, redwngr said:

Hopefully they get a 'cold' check once in a while too. 

 

 

 

Agreed. The longer the oil sits, the more accurate the reading. I wonder if there is any measurable increase in oil volume with temperature changes, for instance the way that transmission fluid expands when hot.

[Grumpy Bear]

1 hour ago, Supreme Pizza said:

 

Agreed. The longer the oil sits, the more accurate the reading. I wonder if there is any measurable increase in oil volume with temperature changes, for instance the way that transmission fluid expands when hot.

 

Yes. New motor oil has a 'average' volumetric thermal expansion of .000389 per *F. Or .0007 per *C. 

 

POA's expand about 5-7% less than mineral based oils. That is of the expansion volume. 

 

A system I am currently working has a 5 quart capacity. Checked cold, no 32 F vs a hot check of say 160-162 F is a difference of 8 ounces. On a warm summer day of say 80 F that would be about 5 ounces. A PAO would be about 5-7% less...roughly a quarter to a third of an ounce. 

 

On a dipstick that is a quart between full and hot about 25% of it's range on a cold day in this example. 

 

There's a calculator for that: https://www.engineeringtoolbox.com/volumetric-temperature-expansion-d_315.html

 

Just use the right units and fluid expansion rates. 

 

Also means I've been overcharging my wife's Terrain. 

 

Thanks for making me look into this.....

Edited December 21, 2021 by Grumpy Bear