The BMW 5 Series E60 (sedan) and E61 (wagon/Touring) marked a major stylistic break under the Chris Bangle era. It introduced a plethora of new technologies (iDrive, head-up display, active steering, Dynamic Drive active anti-roll bars) and made extensive use of aluminum (front end). While its dynamic qualities and comfort are undeniable, this generation is known for its electronic complexity and the extreme variability of its reliability depending on the engine. The March 2007 facelift (LCI) improved interior finish, made the electronics more reliable (gradual transition from iDrive CCC to CIC system), but introduced new direct-injection gasoline (N53) and diesel (N47) engines that would bring their own set of costly problems.
The BMW 5 Series E60/E61 is a polarizing car. A magnificent touring car, it can turn into a financial black hole if poorly chosen. The verdict depends entirely on the engine. For a worry-free purchase, prioritize indirect-injection 6-cylinder gasoline engines (525i/530i with M54 or N52) or the robust 6-cylinder diesel engines (525d/530d with M57), provided the intake swirl flaps are removed and the automatic gearbox history is checked. AVOID N47 diesels (520d post-2007) due to the timing chain, N53 gasoline engines (post-2007) for their direct injection problems, and V8s (N62) unless you have a repair budget equivalent to the car's purchase price. Electronics remain the Achilles' heel of this generation: a meticulous inspection of all equipment and the trunk's watertightness (especially on the E61 wagon) is mandatory.