First and foremost, make sure you have all the PCM updates done. Second, as I've learned there are varying ways to define an "empty" tank: https://www.rx8club.com/rx-8-discussion-3/low-fuel-warning-light-144058/

There are few known good ways to improve you mileage signigicantly, but pre-mixing has definitely proven to improve gas mileage for me - I gained about 2 mpg on average and avoided the summer highway driving power loss issue using this method. 2 mpg improvement by far outweighs the cost of pre-mix in my book. But I haven't been premixing recently, and on my first full tank after the PCM16 reflash I had to low fuel light come on at 220 miles (wow!) and so far none of the power loss symptoms. It may not be entirely due to the reflash since I did have a long (100 miles round) trip meeting this week, but still I was pleasantly surprised to not get the light until 220. That means 250 miles before I refill!

With pre-mix I've seen almost as high as 22 mpg on highway miles . . . and that cruising at 80-90mph mph, but I did manage a best of 310 miles on a tank! I'm sure I may have seen a couple mpg higher if I maintained 65, but I would have had to shoot myself in the head if I did that on that long trip!

 

WOW 50 to the first 1/4 tank I usually see 30-40miles to the first 1/4 but that's inthe city but 50 for the first 1/4 on the highway is about right thats what I get on any interstate trip you are fine and with getting that to the first 1/4 you're shooting for a little over 20 mpg for the trip maybe even up to 23 which i have seen once...

 

I just went on a trip and I drove mostly all highway (98%) and I was able to get 10.3L/100 kms (22.8mpg). I drove between 105-110km/hr (65-68mph)and used no AC. Traffic/Idling seems to be really really really bad for the 8. Might also be the accelerating from a stop that uses a lot of gas.

 

190 - 200 per fill up................................that last me 3 weekends , since it not my DD . If is nice out .

 

Generally it goes like this for me. Around 50 miles at the first quarter tank, 120 at the second quarter tank, 180-200 for the third quarter mark, and about 280 for the full tank. That's in mixed mostly running around driving.

All highway with a well tuned engine, it is more like 65 at the first quarter, 160 or so at the half, 260 or so at the 3/4 mark, and 340 or so at the full tank. That last run would work out to about 23 or 24 miles per gallon. Obviously, the tank isn't empty at the end.

That's what I consider normal for the car ... I also don't have the new flash though.

 

When I was in college, a buddy of mine was dating this really hot girl; a real head-turner. But all he ever worried about was whether she was cheating on him. He never took the time to just enjoy her, and his constant BS ended up pushing her away. Why would you worry about that in college? I don't know.

 

250 on good days 230 on bad days, but definately over 200 per tank