I find with gas guzzlers you end up knowing and trusting your
fuel gauge much more than in smaller cars. I remember leaving Reading once and seeing the reserve light come on and travelled down to London on it because I knew I would have enough capacity to get to my destination. I'm a bit surprised at some of the MPG figures here though, because even driving me S212 really hard in Germany on the autobahn, like over 120mph constantly and having to brake for restrictions and road works, i still managed around 19mpg, when traffic slowed it went up to 28mpg. I always fill up with 98 octane, I don't know if it gets better economy?
Edit: i forgot to add, i don't think the gauge is deliberately dynamic, but I find it takes a while to move off from 100% but then it it's more constant