Sulfated Ash Question

[Best F100]

In regard to the ash buildup, that eventually clogs and plugs up the DPF emissions filters of diesel pickups.

A simple question:

What is the source of the MAJORITY of this ash buildup? A) The sulfated ash content of the motor oil used? or B) the diesel fuel itself, the vehicle uses? So far, of the two people within the oil industry that I have asked, I have a split decision.

As the owner of a ‘16 Chevrolet Colorado with the 2.8L Diesel engine, I am by warranty, restricted to a 5W30 Dexos2, low sulfated motor oil. (Pennzoil Platinum Euro L 5W30 / Mobil 1 ESP 5W30 type oil). If diesel fuel is really the culprit here, it sure would nice to have the options of using Rotella, Delvac or Delo.

 

[kschachn]

FWIW it’s really just the ash content, the term “sulfated” ash comes from the procedures in the standardized test using sulfuric acid.

The ash in this case comes from certain metal based additives present in the oil. The sulfated ash test tests the oil, not the fuel.

 

[CleverUserName]

The ash in fuel is just ash. Sulfated ash comes from the motor oil. Both ash contribute to DPF loading. ULSD Diesel fuel by ASTM standards can have 100 ppm of ash.

I don’t believe ash from engine oil is a significant factor in DPF longevity unless you have an oil consumption problem.

I don’t use Dexos 2 in my 2.0 CDTI Cruze or 2.8 Canyon. I also don’t use VW 507 in my 2.0 VW TDI. In all three vehicles I use CJ-4 10w30, 15w40 or a blend of the two. None of them consume any measurable amount of oil between oil changes.

 

[RooflessVW]

The ash in fuel is just ash. Sulfated ash comes from the motor oil. Both ash contribute to DPF loading. ULSD Diesel fuel by ASTM standards can have 100 ppm of ash.

I don’t believe ash from engine oil is a significant factor in DPF longevity unless you have an oil consumption problem.

I don’t use Dexos 2 in my 2.0 CDTI Cruze or 2.8 Canyon. I also don’t use VW 507 in my 2.0 VW TDI. In all three vehicles I use CJ-4 10w30, 15w40 or a blend of the two. None of them consume any measurable amount of oil between oil changes.

Are you monitoring soot/ash loading?

 

[CleverUserName]

Are you monitoring soot/ash loading?

The TDI and CDTI are both new to me with about 50k miles. I have no idea what the previous owners used in the CDTI or if it was the Dexos 2. I know the TDI got the wrong oil (not 507) as I have the service records from the local garage that took care of it for the elderly man who owned it. The TDI got a new DPF 8k miles ago and has always done a regeneration every 180 miles whether it needs it or not, it must be a default setting programmed for the emissions dieselgate fix.

My 2.8 Canyon has gotten CJ-4 since it’s first oil change @ 1500 miles. It still performs a regen every 300-500 miles based on my driving style. It has almost 40k miles on it. It has averaged 24.3 MPGs since I’ve owned it.

theoretically if all three vehicles burn a negligible about of oil, say 4oz every 10k miles.

4oz x 1.0% SA for CJ-4
vs
4oz x 0.80% SA for Dexos 2

there is a marginal increase in the ash from CJ-4. So it’s possible my DPF may only last to 190k miles. If I had used Dexos 2 it might last to 200k miles. Is it significant considering the lower engine wear with the CJ-4? I don’t think so. If I had an oil consumption problem or operated under continuous high load I know more oil would make it into the combustion chamber and the difference would be more significant, however it’s not a consideration for me.

 

[Stuville77]

I am in no way a tribologist, but in general the majority of soot comes from the additives that are placed in the oil.

The most interesting factoid I came across while doing research was the effect of calcium on soot in DPFs. There's a slide deck at the following link that discusses the impact of Calcium on DPF backpressure. Long story short, Ca-based ash shows much larger effect on pressure drop than Zn ash, or the ash from a CJ-4 HDEO. It also appeared that clearing that ash was the most difficult during regenerations. Given how high the Calcium levels are in some oil, that could be a concern long term. https://www.energy.gov/sites/prod/files/2014/03/f8/deer09_sappok.pdf

The best way to keep your DPF clean is by not burning oil that ends up there. The next logical step would be choices of oil that have lower concentrations of the worst offender elements.

As with everything, there’s trade offs. I can’t plug in my block heater at work, so 5w40 is my oil of choice. That has a higher burn off rate than 15w40, but I need it for cold starts. Valvoline appears to be lower in Ca than others, but makes up for it with Mg and Zn to retain a decent TBN. Members of the forum have suggested HPL for a more stable oil that will stay in the sump. That’s more $, sooo....