I rented a Bimmer when I was there Bram. There are quite a few cars to choose from, but it was my first time on a track so I didn't want to go too crazy. Next time will be a different story. Maybe a 911, at least something with a stick and some more go. I would have been faster in a V6 Accord coupe than that floppy paddle BMW. An S2000 would be a blast there or a NSX of course. Most of my laps were in the wet, on the first lap it was snowing. One of the last laps the track dried out half decent and I stayed fairly close to a couple of guys in a S2000. I would say it wasn't their first time there, so I was happy with that. When you rent the car you are on the hook for up to 6 or 7 grand if you bend the car up good, plus the repairs to the guardrails, tow trucks, ambulances, etc. Needless to say I had to listen to a sermon from the wife before heading out. She wouldn't go with me, and neither would my brother. They were plenty nervous in our rental Merc on the autobahn. They definitely would have crapped a load at the ring.
The regular car rental places apparently often have spotters at the track. If they catch you out there with one of their cars you are blacklisted forever with that company.
