I get about the same (240 miles) on my 94... I fill up between 10 and 11 gallons... .. although this last time I was at 270 miles and only filled up 9 gallons which probably means I could have easily gone 290 or more.. ... that's unusual since my driving hasn't changed but I did do an oil change so that might have helped a bit.. I'll wait and see what I get this time around since I just filled up ..
My 98 gets a little over 300 on a tank in the city. (I always drive it to as little gas as possible, guess I am just supra lazy : ) My highway usually isn't that much better though since in the city my windows are down but on the highway I gotta crank the A/C 24/7.
I think its a 14gal tank and I always end up filling about 13.5 gal in.
21.79 to 25.33, 23.26 "lifetime average" since I bought the car in July. Those are calculated numbers, not guesses. I don't want to say (think about) how far past 40 I am, but it's safe to say this car (98 GLE) is driven pretty easy. The same commute in a 97 Prizm LSi (1.8L)was 32 mpg, but alot less car.
Like RyanDB2 said, I get about 300 miles on a tank. 15.9 gal capacity for a 98 acording to the book.