It all started with the E34 5-Series, and the BMW 525i was the entry level offering for their mid-size executive car. It was powered by a 2.5L straight 6-cylinder engine, and different updates throughout its lifecycle saw horsepower figures between 168-189hp. Because it was the most affordable way to get a piece of BMW luxury, it was the most popular E34 in the world (almost 250,000 sold). The next generation 525i was produced as an E39, which consisted of the same 6-cylinder engine but entirely different chassis and suspension. Rigidity was increased, suspension components were lighter, and steering was more responsive. Close attention was paid to the new BMW 525i parts that went into the E39. The last 525i to be produced was an E60, which definitely had the most aerodynamic chassis and overall design. Power output increased to 215hp by the end of production. Fun fact: Jerry Seinfeld drove an E34 BMW 525i in several episodes of Seinfeld.