Black Diesel oil is normal. The specs you were seeing good have been soot. A bypass filter setup will take care of that. The thing about Oil most people dont realise is that oil does not really go bad, it just becomes contaminated. So, as long as you filter it properly and monitor it for any contaminants that would indicate a serious problem, there is no real need to change it so often.
I spent almost 10 years as a Locomotive mechanic working on engines that cost as much as $800,000 and they NEVER do oil changes on them. Every Locomotive Diesel Engine has a "Lube oil sampling valve" that can take a sample mid stream in the oil. This is done every 92 days and the sample is sent to a lab. As long as the lab shows no signs of serious contaminanats (Fuel, coolant, etc. ), the oil will not be drained. All we would do is change the filters (There are 10 in a large housing plus 2 strainers) every 92days. I have seen locomotives with hundreds of thousands of miles with the original oil. Not to mention how many hours they sit idling (WEEKS at at time!!). It is just topped off when nessecary. The average lube oil capacity in a Locomitive is about 400 gallons. This acts like a buffer against small quantities of contaminants. An ISB only has 11 quarts, so i would not go with NEVER changing the oil in one. I know the Ram is does not have a Locomotive engine (It would be cool though)But they are both diesels, and that is what matters.
In a Ram that is not "Beaten" on or towing constantly, you can EASILY go 7,000 miles between oil changes. That is actually a minumum. Changing it more often then that is honestly wasteful (This is fact, not opinion). The oil has barley begun to start picking up exxcessive dirt. And if you are using good filters like the Stratapore, you are fine. Diesels burn alot cleaner then gas engines, its just people see black oil and think its really dirty, but its not. That interval can be extended even longer with the use of a Bypass setup, and even longer still with the use of Synthetics. If you dont mind changing your oil every 7-10k miles then a Bypass filter or Synthetics are not worth the investment. But if you plan on driving long distances and dont want to have to find a place to do oil changes, or are just too busy. A Bypass system and Synthetics can extend you drain interval to 20k miles or more. Provided you are doing lube oil samples. This is a MUST if you are going to go to extened drain intervals since a serious contamination problem will not be noticed and will do damage before your next oil change. That is the key to extended drain intervals, the sampling. Every 6-10k miles is good, and be sure NOT to get samples from anywhere there may be sediment, like the drain plug. You will get inaccurate readings. Use a dipstick sample kit of a sampling valve.
Oil standards have gotten so high and engines are running so clean that 3K miles oil changes are really not nessecary anymore. Even Dodge reccomends 7k oil changes. The only people who think this is a BAD idea are the oil change places like Jiffy lube, and i Dont think i have to tell you why they think its a BAD idea. I have an Amsoil dual Bypass and i am running Rotalla 15w-40 and doing 10k oil changes. My last sample came back fine. I could have left it in longer. The Cummins is so easy to change the oil on since the ground clearence is so high that i keep wanting to change it more often, just to have something to do. I try and resist the urge and spend the money i would use for oil and filters someplace else. We are changing our tow trucks oil every 10k miles and these trucks are towing EVERY DAY in stop and go traffic and are usually being driven by young aggressive drivers who dont know the meaning of "Take it easy"
There is alot of information on this subject on other threads and other websites. Its worth checking out.
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