I've noticed a few people saying they've done this rather easily without pit-stops and using a reasonably powerful car with Racing Softs equipped.
Personally, I've done this also, but only the once, as it was
TOO EASY!
These days I race around '
The Ring' in a
Corvette ZR1 (C6) LM Race Car. It's obviously not the fastest car out there, nor is it the greatest for all things pertaining to driving Nurburgring, but in saying that, it's suspension (when tuned nicely) is a perfect ride, and the torque is all you need, one little drawback is of course the weight, but again, when tuned up nicely, it will do a lap of the FULL Nurburgring in under 8 minutes rater easily, even in the wet.
I like to play around each time I do this race, sometimes I pit each lap, sometimes only on lap 2 for fuel. Other times I'll grab fresh tyres each time, and even when in the mood, I'll chuck on some 'Inters' just for some drifting fun within the race. I still end out beating my nearest opponent by 2:15/30 even when pitting each lap. So it's entirely up to the user on 'how' they wish to race this.
If you are still in a beginner stage, I'd suggest Racing Softs, all the way, pitting at the end of lap 2 for Fuel (and possibly new tyres, if you've managed to wreck you current one's :-S) and a decently powered car, with great weight ratio's.
Otherwise if you and intermediate to advanced, then I'd suggest doing whatever floats ya boat, as we all race differently and our setups will all be (within tolerance) different also. So pick a decent car, chuck on some Racing Soft tyres, and go to you hearts content