Review-OnRoad You need to work the 2.5-litre V6 petrol engine hard to extract maximum performance, but it pulls cleanly from low revs and is punchy enough for assured overtaking. Similarly, the diesel is fine at low speeds, but the gearing is too long and you often find yourself going from sixth to fifth to keep up with motorway traffic. The V8 petrol engine in the high-performance IS-F model is sensational, however, churning out 417bhp and hurling the car from 0-62mph in just 4.8 seconds.