I think I remember 25 litres being mentioned for the bigger tank option in the 5Exi. That fits with quantities I remember filling up with. Still too small really - I keep wondering where I could fit another 10 litres or so of capacity in.
Honda k20a2 - 200 miles is do-able on the road quite easily it seems (not sure quite how close that is to empty), and about 70-100 on track I'd estimate.