Funny I noticed this also. I wonder if it's because of the material that you see the oil on, on the dipstick. It's not just the metal of the dipstick like a lot of other cars. In the old days I've heard that if the oil gets dark, that's good because the oil is holding the dirt in suspension instead of depositing the dirt on the cylinder walls ect. Not sure how true this really is, if at all.
I just looked again, the oil level may be increasing and i saw someone else say the same awhile ago. I,m going to keep a better eye on the level. I don't think the dipstick material makes any difference.
I don't think much of that guys opinion. I've had several Prii and each one had very clean oil between oil changes until that got approx. 120k mi. or so. None of them burned a drop of oil between 10k. mi. changes. The last one I had only started using a quart and a half between changes when it had 150k. mi. on it. I traded it for my Niro when it had 166k. mi.
Telling anything about oil or the engine by looking at the oil is like telling the age of a woman by looking at her dog.
Blackstone will analyze oil for a fee and give a much better indication of oil and engine.
Having said that, I wonder about Niro oil. It leads an easy life by running less per mIle than conventional cars, particularly the plug in. However, cold starts and initial higher RPM running is really hard on oil. It seems like those two factors might compensate for each other to some extent.
I haven't experienced oil level increase but have detected an occasional fuel odor that might well be coming from my Niro.