Last year I did 2900 km during my vacation in Germany and the surrounding countries. Having previously experienced Autobahn driving at least 4 times, I decide that this time I would rent a nice car. There is nothing worse than being in some 1.1 liter econobox trying to break 150km/h in the right lane. I reserved an E class. However, when I got there, they did not have one available. So I got a 5spd. BMW 520i. This was my first time driving that particular model. I must admit I was very surprised by this car. That tiny inline 6 impressed me with its top end. I am used to driving cars that take a little while getting from lets say 100 m/h to its top speed. This car was adequate for off the line acceleration ( European magazines quote 9+ sec 0-60 times). But if you are at 180 km/h and you punch it, it flies. I was very happy cruising at 220km/h(135 mile/hour) for long periods of time. At that speed, you are at almost 6000rpms ( the redline is at 6250 so there was still some room ). My point is that this 150hp little engine was able to accelerate a 3400lb automobile (2 passengers plus luggage added another 400 pounds) from about 5000rpms to 6000rpms like I've never experienced with my Euro 190 2.3-16. The additional benefit is the sweet sound and it was soooooo smooth. Great fun!!!
I thought I'd share this story. Also, if anyone is planning a trip and wants to experience the Autobahn, you should try to fly Lufthansa. You can ask the airline to connect you with Sixt - the biggest rental company in Germany. Because of their agreement with Lufthansa, they should give you a deal. In my case, the best price I was getting from other companies was close to $800 for 12 days. Sixt was able to give it to me for $450. That is less than $40/day for a luxury class car.

Best to all,
Alex