Whats with the 40L tank?? 250km out of 40L is not all that bad...its not great, but not bad. I regularly get 400-450km out of 60L, where you would be getting ~375km.
The fuel gauge in the R33s is a little deceptive. The empty line does not actually indicate a full quarter. Mine usually does 350km when the needle hits the empty line, then 50km later the fuel light comes on. I can usually drive around for 30-50km with the fuel light on.