I took my 2002 Jetta TDI wagon to a neighborhood shop about 10 miles, 24 hours ago. They supposedly changed the oil, but the color is very dark, almost black. Definitely not light-colored/transparent. The oil change was performed along with other work (replacing alternator & brake pads).
I'd run it back right away without a thought, but I'm wondering if this is normal for a 10-year old diesel car with 175,000 miles on it. Last oil change was made around 10,000 miles ago. The engine is original, too.
Not sure if this is relevant, but I always have 5% to 99% biodiesel and Diesel Kleen in the fuel tank.