2006 Audi S4 vs. 2003 BMW 645
To start off, 2006 Audi S4 is newer by 3 year(s). Which means there will be less support and parts availability for 2003 BMW 645. In addition, the cost of maintenance, including insurance, on 2003 BMW 645 would be higher. At 4,398 cc (8 cylinders), 2003 BMW 645 is equipped with a bigger engine. In terms of performance, 2006 Audi S4 (340 HP @ 7000 RPM) has 15 more horse power than 2003 BMW 645. (325 HP @ 6100 RPM). In normal driving conditions, 2006 Audi S4 should accelerate faster than 2003 BMW 645. With that said, vehicle weight also plays an important factor in acceleration. 2003 BMW 645 weights approximately 180 kg more than 2006 Audi S4.
Because 2003 BMW 645 is rear wheel drive (RWD), it offers better handling in dry conditions; in addition, if you are looking to drift, it will be much easier to do with 2003 BMW 645. However, in wet, icy, snow, or gravel driving conditions, 2006 Audi S4, being front wheel drive (FWD), will offer much better control with better grip. With that said, do keep in mind that many other factors such as speed and the wear on your tires can also have significant impact on traction and control. Let's talk about torque, 2003 BMW 645 (450 Nm @ 3600 RPM) has 40 more torque (in Nm) than 2006 Audi S4. (410 Nm @ 3500 RPM). This means 2003 BMW 645 will have an easier job in driving up hills or pulling heavy equipment than 2006 Audi S4.
Compare all specifications:
| 2006 Audi S4 | 2003 BMW 645 | |
| Make | Audi | BMW |
| Model | S4 | 645 |
| Year Released | 2006 | 2003 |
| Body Type | Station Wagon | Coupe |
| Engine Position | Front | Front |
| Engine Size | 4163 cc | 4398 cc |
| Engine Cylinders | 8 cylinders | 8 cylinders |
| Engine Type | V | V |
| Valves per Cylinder | 5 valves | 4 valves |
| Horse Power | 340 HP | 325 HP |
| Engine RPM | 7000 RPM | 6100 RPM |
| Torque | 410 Nm | 450 Nm |
| Torque RPM | 3500 RPM | 3600 RPM |
| Engine Compression Ratio | 11.0:1 | 10.5:1 |
| Acceleration 0-100mph | 5.9 seconds | 5.9 seconds |
| Drive Type | Front | Rear |
| Number of Seats | 5 seats | 4 seats |
| Number of Doors | 5 doors | 2 doors |
| Vehicle Weight | 1510 kg | 1690 kg |
| Vehicle Length | 4590 mm | 4830 mm |
| Vehicle Width | 1790 mm | 1860 mm |
| Vehicle Height | 1420 mm | 1380 mm |
| Wheelbase Size | 2660 mm | 2890 mm |
| Fuel Consumption Highway | 11.2 L/100km | 8.6 L/100km |
| Fuel Consumption City | 15.7 L/100km | 17.2 L/100km |
| Fuel Consumption Overall | 13.8 L/100km | 11.7 L/100km |
| Fuel Tank Capacity | 63 L | 70 L |
