I recently bought a Diesel A4.
The oil in the engine was like crude oil which I quickly replaced with 5/40 fully syn + filter.
Although I poured in golden oil it was instantly black and mucky on checking the dip stick..
3 weeks + 1000 miles later I have just done another oil change.
I instantly checked the dip stick and it was golden until I drove the car and its black again.
Have I so much crud in the engine that I need to do a few changes to run golden or being a Diesel engine it just will never run golden!?