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Audi recommends a 10,000 mile interval using conventional oil. I decided to run Mobil 1 5W30 (couldn't get 0W40 at the time). Here is the report from Blackstone Labs.

What do you think?? I now Castrol Syntec 0W30 (VW approved ACAE B3, etc) in the crankcase for the next interval.
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This is not scientific but I've noticed that when changing brands of oil. The first run of a new oil sometimes reacts with the leftovers from the old oil. Causing the TBN to drop faster on the first sample of new oil than the second run sample. Thisd I've seen in analysis posted elseware and in my own oil analysis.

I noticed this in my own VW TDI when I was changing from VW factory fill 5w-30 to Schaeffer's 15w-40. The TBN dropped much slower on the second round of Schaeffer's as compared to the first round.

First analysis 10k on vehicle 5k on the Schaeffer's TBN 6. Second analysis 20k on vehicle 10k on the Schaeffer's TBN 9.
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