What would cause black oil in a tuned engine

[Unilevers]

870's are very hard to get clean and stay there. they are older engines with older parts and have a very slow acting VGT which makes them slightly less efficient and that translates to darker oil quicker.

your fuel mileage also has a direct correlation to how dark your oil is and how fast it changes. the higher the mileage the cleaner it will be and vice versa. What you pull and duty cycles and condition of the engine also play big roles. the fct that your oil is staying clean for 10000 miles on a 870 is fairly impressive by itself.

Uni