This is an update on my fuel consumption.
I have my 8 for 2 weeks now, it has 1050 kms (630 miles). It's a Canadian model.
So I tested to see exactly how much mileage I would be getting from a full tank with the following results from the trip odometer;

- Low fuel warning light came up at 335 kms (201 miles)
- Drove to the nearest prefered (Chevron) gas station at 370 kms (222 miles) and had 6 litres left since the whole fill up was 54 litres out of a 60 litres tank.

That was actually a little scary since I had no certainty of how much litres was still left in the tank once the warning light came up. This also happened on the highway... so needless to say that I was doing 120-130 km/h (72-78 mile/h) in 6th gear the whole time.

Therefore with my numbers and with Mazda specs for the RX-8 of 9 litres/100 kms, my calculation tells me that once the Fuel Warning Light comes up there should be an approximate 10 litres of gas left in the tank, resulting in about 100 kms (60 miles) to find the closest gas station.

In conclusion, I would have to say I'm pleasantly suprise I can get this much mileage from my 8. My expectation was in the low 300's kms (180 miles) but it seems that I will be able to get around 350 kms (210 miles) from a tank.
Although I hope this numbers would be of good reference to some people, please do not rely solely on them as these are only meant for informational purposes. You should still gas up as soon as the warning light appears.

One more thing, throughout the tank my driving was generally normal driving. I kept my RPM below 4500 shifting before that point. I did get however a few 7000 RPM rev but not much, sometimes it's hard to restraint yourself

 

My low fuel light comes on at around 200-210 miles on the tank, after which I drive around 30 miles max before filling up. Which gets me fairly consistent 14.5-14.75 gallon fill-ups at between 230-240 miles. I don't push it much further than that, since I have run out of gas at 252 miles. So I guess my numbers match up to your's fairly well.

This is for my typical driving around town in the Northern Virginia area. On all-highway driving I can push 280 miles on a tank at 80-90 mph speeds (I find it hard to drive this car much slower than that!). My car has almost 9000 miles on it now.

 

My fuel light came on at about 230 miles and i pushed it to 247. I think i could have gone to 252 with know problem but i did'nt want to push my luck. I am sitting at half a tank now with 130 miles so lets see what i get this time

 

I'm wondering, does the fuel warning light flashes at the end or does it remains constant?

 

it turns on and is steady. No flashing.

 

I recall someone pointing out awhile back that not all the gas left in the tank is necessarily available for use because the tank is saddle-shaped; some may be trapped on the wrong side. I've been fighting the urge to just roll for awhile after a warning light for that reason.

I tend to get the light at 215 or so miles in city driving.