Here is the latest oil report on my Cummins using Mobil Delvac 1 5W-40 full synthetic oil from Blackstone Laboratories.

In service 10/17/03, drained and sampled 8/24/04
Miles on oil:17,134
Miles on engine:111,366
Oil filter:Fleetguard StrataPore
Air filter:Amsoil oiled foam
2 oil filter changes throughout the service interval, approximately 2 quarts make-up oil added.

Elements in ppm:
Aluminum 5
Chromium 3
Iron 26
Copper 3
Lead 3
Tin 1
Molybdenum 1
Nickel 0
Manganese 1
Silver 0
Titanium 0
Potassium 3
Boron 32
Silicon 5
Sodium 3
Calcium 2888
Magnesium 475
Phosphorus 1195
Zinc 1451
Barium 0

Properties:
SUS visc@210F 74.6(40 grade)
Flashpoint 450F
Fuel <0.5
Antifreeze 0
Water 0
Insolubles 0.5%

Looks like I could have run it longer. I used several tankfuls of 5% Bio-diesel fuel this spring and summer, to give it a try, and it hasn't affected the oil.

I used the full synthetic for it's cold weather flow. This particular oil is also badged as Mobil1 Truck and SUV oil now, and I was able to purchase some more of it at a local Fleet Farm store for $4.59 a quart.
That's less than what I paid for gallon jugs of the stuff.

And, as always, the Cummins is easy on oil.

 

Yeah, you might as well push it out to once a year, it looks nice at 10 months. I'm doing yearly changes on dino based on analysis, but I only run about 8k a year.