We had a spot of nice weather on Sunday evening so we went for a drive down the autobahn:
The car had one passenger and half a tank of fuel 50/50 split of Shell Optimax 100 and Aral (BP) Ultimate 100. No particular reason for the split other than locality of filling stations.
Unfortunately you can't see the speedo on this video (you can on the original) but here are the figures:
Car speedo: 179mph
Garmin c330 Sat Nav : 168mph
Garmin eTrek H GPS: 165mph
Obviously the speedo is very out and I'm guessing the true top speed is between 165 and 170mph. Not bad.
Edit: Forgot to add this: