There are 1 owner-reported engine complaints for the 2015 Audi S4in NHTSA's database. These are unverified consumer reports and may not reflect confirmed defects.
The R&R valve/oil separator unit failed on my 2015 Audi S4 at approximately 71,000 miles. This unit, when fails, can mix the oil and anti-freeze which can seize the engine. I was able to catch the problem before engine failure. Minneapolis Audi repaired the vehicle this week, 1/10/23. There were NO warning indicators except noise. Various media sources have stated that this is a known engine failure concern between 60-90K miles for this engine. Audi does not recognize this as a safety or warranty concern.
Complaints are unverified consumer reports submitted to NHTSA. A high complaint count may reflect vehicle popularity, not defect severity. Data sourced from NHTSA public records.
Data synced from NHTSA on Apr 26, 2026