Duramax 10k on Rotella 5W40 (pre T6) w/6% fuel

[npauli]

All,
Just changed oil at 10k and got the results back. All looks good to me except fuel in oil. Here's the results at 5k & 10k

Mi. on unit: 65,556
Mi. on oil: 4,908/10,011

Oil type: Rotella 5W40 (CJ4, not T6)
5k miles/ 10k miles
Cu: 2/4
Fe: 5/7
Cr: 0/0
Al: 0/1
Pb: 2/3
Sn: 0/0
Si: 4/4
Na: 1/2
K: 1/2
Mo: 50/49
Ni: 0/0
Ca: 1009/985
Mg: 1063/1013
Zn: 1259/1013
P: 1078/1012

soot: 0/0
oxi: 18/18
nit: 7/7
sul: 19/19
H20: N/N
glycol: N/N
fuel: N/Y
% fuel: NA/6.18
V100: 13.0/12.0

I found out recently that they don't report % fuel unless it's "high" or if you ask them to. The fuel might be from a bad injector, but I'm guessing it's just from running all winter with very light loads. I try to drive for good fuel economy, so the loads are always low.

Q) Since I didn't get % fuel reported at 5k, can you infer anything from the V100 to tell me if I had fuel in oil then? It would make me feel better if I did - less likely to be the injector if it's making oil at this slow of a rate.

FWIW, I recently got some fantastic fuel economy on a 100 mile trip (>29 mpg ~ 55 mph), and I wonder now if having a ligher oil could have played a role.

Trying to decide when to pull the next sample. Another at 5k, or sooner? Oil in it now is more of the same (last of my stash) Filters are M1.

 

[DieselTech]

LB7's have always had injector problems, looks like you may have one leaking a little. GM did increase the warranty on LB7 injectors to 200K

 

[dnewton3]

Time for an OCI if you haven't yet. The oil was doing a great job, but assuming the fuel is correct, you need to get it out of there now.

What generation of Dmax is this truck? As stated above the LB7s have injector issues and have an extended factory warranty for them. Take this report and show them the fuel reading a press for injector checks/replacement.

 

[npauli]

I did change the oil the same time I pulled the sample.

Yes, this is the LB7, infamous for injector problems. The extended warranty is 7yr/200k mi, and I'm past the 7 yr mark.

I've also posted this at a GM diesel forum and a hypermiling forum to try to estimate the probability of injector problems vs. more benign causes, and so far I don't think it's injectors, but it's a possibility.

Can anybody tell me if 13.0 viscosity @ 5k says anything about the presence/absence of fuel in oil?

 

[DieselTech]

Are you presently running any aftermarket tuning? 6% in 10K isn't bad but it isn't good either. If you have an injector leaking down after shut down you and nobody else will be able to diagnose it. I belive from the UOA thats what you have going on. Instead of new injectors industrial injection does a great job of remaning and it's about 1/2 the cost of new. I have never had an industrial injection injector fail.

 

[dnewton3]

This product is a II+/III group rather than a PAO, so there are a LOT of VIIs to get that 5w-40 spread. Some amount of shearing in regard to grade is simply expected. Hard to know exactly how much is due to fuel dilution. If I'm reading your report right, your Vis at 5k was 13 and at 10k was 12? I'd say 6% fuel is contriubuting for sure. Question is: how much is due to fuel? 6% fuel is more than I'd want to see.

The thing to keep in mind is that the loss of Vis, and even fuel dilution, have not seemed to hurt the engine with increased wear numbers. Still - the pragmatic approach would be to get the dilution resolved, and then continue to track for a short while.

 

[Oldwolf]

Soot level of 0 is amazing.

 

[Jim Allen]

Yeah a good report, alright. Zero soot? at 10K? Wow! DIdn't think that was possible but on a clean running electronically controlled diesel with stock tune and driven for MPG, I guess I can see it. I agree that job 1 is getting those injectors fixed.

 

[addyguy]

Even with 6% fuel, wear is really, really low, and the oil only just went out of grade. Not a bad showing at all.

 

[Pablo]

What lab is this? I kinda doubt the 0% soot and the numbers don't look right.

 

[npauli]

The analysis was done through the local Caterpillar dealer.