I know how you get 10 mpg. All you need to do, is get out of 3rd gear all the time on freeways. Use 4th, 5th, 6th. Can go from 10 mpg to 14 mpg like magic over a few tanks.

^ha ha yeah that would prob drop the mpg also

Short Trips
 

In my experience

3-5 mile trips (With no real warm-up)
Track days
1 Flood
Driving it hard
Testing (Not moving)
Air filter done

My car after 4.5 years and 97800 miles, has a lifetime average of 17.8 MPG
9 MPG Low
22 MPG Hi

LA Traffic (LB to BUR + Local mostly) 17-18 mpg
9 long trips 19-22 mpg
2 Track Days 9-12 mpg
5 Club runs 16-17 mpg
Local (3-5 mile lunch’s at work, 5-10 mile trips from where I live) 12-14 mpg

I too have been getting pretty poor mileage out of my RX-8 and have done everything under the sun to improve it. Let me share what I have learned over the last 3 years.

- The RX's mileage is heavily depended on the traffic you encounter. I drive Chicago City driving. If traffic is light I can get around 14mpg, if traffic is heavy that can drop to 11mpg.

- Winter temperature will hurt the mileage by 1 to 2 mpg depending on how cold. I have hit 10mpg in winter.

- Keeping the revs down will help the mileage considerably. Reving it out will drop your mileage by 2mpg.

- Highway I have gotten as good as 22mpg but with spirited driving I average 18 to 20mpg.

- Octane of the gas has no effect on mileage or power.

- Higher inflated tires, high performance air filters, synthetic oil all produced no increase in mileage.

- The best way I found to increase my mileage was to in install a scan gauge. It is a $100 device that lets you monitor a various of readings that the RX would normally not show you. You can monitor exact engine temperature, fuel consumed, ect... The most useful gauge is the MPG trip gauge. This will tell you what your current MPG is for a trip, you can watch it fluctuate with different driving and it has shown me how to optimize my MPG. With this device I have watched my MPG increase 2 to 2.5 MPG.

Hope this helps, also if your interested I have tracked my mileage at every fill up and would be happy to share this with anyone who wants it.

Final word the RX-8 is a gas hog, it will consume gas at 2 to 5 MPG more then any of its competitors depending on the type of driving, so always keep that in mind.

I get between 10-12 in the city and 20-22 on the highway.

I drive my car like it was meant and designed to be driven....like a sports car!

When I want to save on gas I switch over to my Suzuki DL650 V-Strom which gets @40-45mpg in all conditions.

Anyone considering an RX8 should know going in that the MPG is poor. Worrying about and trying to eke out as high as possible MPG by NOT driving the car like it was meant to be driven seems silly to me. That said I will not complain if I see some improvement when I get an AP, but that is not why I am going to order one. :)