Inside the Audi RS4.
The B7 and B8 RS4 share the 4.2 V8 FSI — a high-revving, naturally aspirated V8 that's arguably one of the best engines Audi ever built. It also has known cam-follower wear on high-km cars and a specific timing chain guide issue that becomes catastrophic if ignored. Every 4.2 V8 FSI through the workshop is inspected for both. If wear is present, we quote head work or engine-out chain work openly — not deferred to sell later services.
The B9 RS4 (Avant) is an entirely different car — 2.9-litre biturbo V6 shared with RS5 and Porsche Panamera 4S. Modern, torque-rich, and very responsive to Stage 1 flash tuning. Warranty is a real conversation. ZF 8HP eight-speed needs fluid on interval — non-negotiable on a car making this much torque.
For a B7 or B8 RS4 approaching high km without a documented chain-guide inspection, we recommend one before you buy or as soon as you own it. Cheaper than a bottom-end rebuild by an order of magnitude.

