You have identified my quandary.

I did a first oil change somewhere below 2K, and planned on intermediate changes. But 4,000 seems a bit low, even though diesels typically need more frequent oil changes due to soot and more blowby.

So here I am with 4K to go with eight quarts of oil and a filter in the garage, and wondering if I should change it. If it wasn't for the indicator, I'd probably be changing it every 6K or so.