2003 BMW 645 vs. 2006 BMW 550
To start off, 2006 BMW 550 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 4,801 cc (8 cylinders), 2006 BMW 550 is equipped with a bigger engine. In terms of performance, 2006 BMW 550 (360 HP @ 6300 RPM) has 50 more horse power than 2003 BMW 645. (310 HP @ 6000 RPM) In normal driving conditions, 2006 BMW 550 should accelerate faster than 2003 BMW 645.
Both vehicles are rear wheel drive (RWD) - it offers better handling in dry conditions; in addition, if you are looking to drift, both vehicles do the job better than front wheel drive vehicles. 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, 2006 BMW 550 (488 Nm @ 3400 RPM) has 38 more torque (in Nm) than 2003 BMW 645. (450 Nm @ 3600 RPM). This means 2006 BMW 550 will have an easier job in driving up hills or pulling heavy equipment than 2003 BMW 645.
Compare all specifications:
| 2003 BMW 645 | 2006 BMW 550 | |
| Make | BMW | BMW |
| Model | 645 | 550 |
| Year Released | 2003 | 2006 |
| Body Type | Coupe | Sedan |
| Engine Position | Front | Front |
| Engine Size | 4398 cc | 4801 cc |
| Engine Cylinders | 8 cylinders | 8 cylinders |
| Engine Type | V | V |
| Valves per Cylinder | 4 valves | 4 valves |
| Horse Power | 310 HP | 360 HP |
| Engine RPM | 6000 RPM | 6300 RPM |
| Torque | 450 Nm | 488 Nm |
| Torque RPM | 3600 RPM | 3400 RPM |
| Engine Bore Size | 92 mm | 93 mm |
| Engine Stroke Size | 82.7 mm | 88.3 mm |
| Engine Compression Ratio | 10.5:1 | 11.0:1 |
| Drive Type | Rear | Rear |
| Number of Seats | 4 seats | 5 seats |
| Number of Doors | 2 doors | 4 doors |
| Vehicle Length | 4830 mm | 4860 mm |
| Vehicle Width | 1860 mm | 1850 mm |
| Vehicle Height | 1380 mm | 1470 mm |
| Wheelbase Size | 2790 mm | 2890 mm |
| Fuel Consumption | 8 L/100km | 10.2 L/100km |
| Fuel Consumption City | 16.1 L/100km | 14.7 L/100km |
| Fuel Consumption Overall | 10.9 L/100km | 12.4 L/100km |
| Fuel Tank Capacity | 70 L | 70 L |
