Amsoil Diesel Oil 5W-40 (Signature Series Max-Duty Synthetic)

[phlfly]

From oil testing - explanation of the results for the fuel in the system.

"Because #2 diesel fuel typically has a viscosity of around 1.9-4.1 cSt at 40°C, which is thinner than a typical 15W40 engine oil with a viscosity of around 14.7 cSt at 100°C, fuel dilution reduces the engine oil's viscosity. When the oil's viscosity is lower than one (1) cSt from the known starting viscosity of the oil when new, we will confirm fuel dilution by ASTM D7593 GC method, reporting the result as percent by volume. However, if lubricant grade is not included with the sample, fuel dilution will be confirmed by GC if viscosity is below 13.3 cSt for diesel engine oil and below 9.8 cSt for gasoline engine oil. If viscosity is above the oil's mid-point for the grade, fuel dilution will be reported as <1.0%."

So that 8% can be just because the oil dropped to 12.5 cst that is about 3 sct drop as new oil (15.4 cSt at 100 ºC).

My question to specialist here - does it lot if after 9,000 miles 5.0 liter diesel engine lost 3 cSt?

 

[bismic1]

SAE 40 weight viscosity range is 12.5 to 16.29 for a point of reference. That said, the diesel fuel can introduce contaminants and is potentially detrimental to other (desirable) physical properties of the oil (ie solubility changes can impact detergents and dispersants). Oxidation can increase also, so TBN is something to watch. From my perspective, the turbo is the first to complain about fuel dilution.

 

[phlfly]

Unfortunately, it's very hard to say what is injector failing. The engine has no codes on fuel system as I checked with Autel. Not sure what is next. I have warranty from Zurich and it's covering fuel injectors. How I can make a case to replace injectors even no evidence on misfire? Any ideas?

 

[mattd]

It can also be from in cylinder dosing for DPF regeneration. Ford and Cummins still use it (excluding ISX and larger Cummins), the duramax has a 9th injector in the exhaust system.

 

[phlfly]

Yes that is right I didn't think about, but during re-gen it will a noticeable increase power. That is kind a good explanation and would make sense.
So I might have to reduce 5K to 6K oil changes, unless to get a "weight loss". I will do another 1K on this oil and to do a rest, another 2 K and do a test. So just make a trend of this.

 

[phlfly]

Retest came with 6% fuel delusion. So I will retest this in 3K miles and see the results.

 

[addyguy]

If these engines do have weak bottom ends, all that fuel and thinning will wipe out the bottom end again. Wear is very high…good luck.
I thought Cummins made good engines, they have a rep for that, sad to see this is not the case!

 

[phlfly]

Yes that is one of the course for cracksfaht bearing. But its not just that, bad oil , failed injector , over torque as this engines never had attempt to produce so much power, Nissan did this on his own way so they bought all rights from Cummins. Cummins told me when I replace engine 1 they would replace engine for free but Nissan owned all right so they could do much about. I think 5 k it's when oil good to go. I will post results after 2k I'm now at about 1k