The X2010 Is faster than any other car.
XP/min increase the faster the laps.
For timed races, yes. I believe the GT5 Matrix is based, or at least supposed to be based, on X2010 times (Edit: Or rather, on the times using the fastest car you can use for the event). For the DCC Nuerburgring, as example, it has listed 16 minutes (15:60 actually) as finishing time. I always use my X2010 and I've never actually finished in 16 minutes, but closer to 17 minutes. And if you look at Tokyo, for example, it lists 15:50. I tend to finish Tokyo in the X2010 in under 12 minutes. For the last race I've done I've calculated the xp/min at 3100. That's the highest xp I've seen for your overall B-Spec level. Yet, individual drivers don't collect xp in the same way, they collect more xp in endurance races than they do in DCC races, due to the multiplier in races where you can race more than one driver.
hang on so you'r basing it on the fact that you think you get More Xp the more drivers that were in the event
First of all, this thread is not about your overall B-Spec level. It's about the quickest way to level up a driver. Given I was doing a single 4 Hour Nuerburgring and then a single 9 Hour Tsukuba and that brought my driver from low 39 all the way to 40, my driver must've gotten a lot more xp than what I was expecting to get. So I browsed the board, and quite a few people came up with the idea that the xp on offer for drivers is the xp of the race times the multiplier. I guess the logic is that your drivers are meant to advance at the same pace as you, and if you need to advance all four drivers by the same degree, then you need to hand out xp times 4. But, it's not actually equally divided over the participants, it seems it's divided based on how much each of them races. And if you only race one driver that driver gets the xp you get times 4, or whatever the multiplier is for the race. I've done a race with x1 and got the xp of the race, I've done one with x2 and got double the xp of the race. And I know that the 4 Hour Nuerburgring and 9 Hour Tsukuba I did paid out about x4, as I needed about 6.5 Million to reach level 40 and I got it with the two races.
Based on that, the Top 5 I posted are the best ways to level up a driver as quickly as possible. And that's what this thread was meant to be about.
Edit: Just finished another 4 Hour Nuerburgring, and while I can't give you any exact numbers, I seem to have gotten around the 2.7M I was expecting. So yes, it really does seem to be xp of the race times the multiplier.