oil sample?

You'll see your mileage improve a little bit too.....

 

One thing that is missing from the oil sample that is critical to knowing how long it can go is TBN test. That is how you tell how much of your additive package part of the oil is left in relation to what it started out with. Most CJ-4 oils are in the 8-10 range starting out. You never want the TBN to go below 3 without changing the oil. This is how you know how long you can go between drains..... how much of the additive package is left.

The viscosity is getting to the low end of a 15w40.... 13.8. It is going outside of viscosity at 13.1. It starts out in the 14.5 range. So it is about half way to going out of viscosity range with this sample. Never understood Cat's soot rating. Is that a ppm? Most labs show percentage such as 2% or whatever.

 

Not sure at this point why your oil is losing viscosity this early on. There is no fuel dilution, so something is stressing and "shearing" those molecules in the oil to cause the loss of viscosity. And you notice a slight oil pressure drop over time, and that is indicative of the viscosity loss the report showed. Oxidation can have some effect on viscosity. Your Oxidation does not look terrible, but not the best either. All you can do is continue to track and watch how things trend.

There is not usually a correlation between oil viscosity and TBN. Usually the correlation is between TBN and TAN (Total Acid Number). Since TBN is the level of additive package of the oil and will usually drop as TAN rises over time.

 

OK, a couple things I noticed in your oil sample, high iron and high silicon, (dirt).

I'm guessing you spend a lot of time in a dirty environment and the air filter hasn't been changed in a while, (explains high silicon), but the iron is really kinda up the for the really short mileage you have on the oil....and the other metals are low by comparison, which is good...

I would change the oil and air filter, run it for 1 day, get an analysis, run it for a week, get an analysis and see how those numbers compare...

On the bright side, the other wear metals look pretty good.

I'm thinking that air filter hasn't been changed in a while.....

 

Ok, your viscosity is normal. (13.8. ) Value should be between 12.4 and 15.3

Am I seeing the mileage on the engine correctly? 123,676

 

I would watch the silicon and when it gets above 5ppm, change the air filter. (I'm thinking that if you do this the iron wear rate will drop accordingly.)

I would also suggest that extended drains are not advisable due to the harsh working conditions. Once a month on the oil change is probably the right schedule. If you spend a lot of time idling that would account for the soot level. I would check with the testing lab and ask them for the soot level expressed as a percentage. The Mobil Delvac can suspend 5% before the soot starts falling out of suspension. Soot falling out of suspension is not good.... That soot percentage will be a big determining factor regarding the oil change interval.