I think I have seen ~4 mpg from HPDE's.

 

I don't let my car drive under 3K except for on the highway and I can average 18 - 20 mpg. You have to remember that as your RPMs increase your AFR increases causes better fuel efficiency. And since you really shouldn't be doing 55mph in 6th gear...your argument there fails as well.

 

ermmm...no...just that cruising around at 40mph in 3rd has given me better gas mileage than in 4th.

 

Remedial reading required.

My first sentence recommended 6th gear (overdrive) cruising on the highway.

My discrete second sentence recommended that if you can bring yourself to slow down then that is best.

They were not meant to be contiguous recommendations, although you certainly can go 55 mph in 6th. However I always find the manufacturer's shift-point recommendations very conservative. I prefer 4k rpm in 6th.

 

"Don't exceed 3k in any gear" That's pretty cut and dry there. What I was saying is the complete opposite. Anything under 3K is underpowered for acceleration and can cause some serious car problems if you keep it up. I prefer to cruise at 4K and have seen better gas mileage by doing so. 6th gear should be used for cruising distances on a highway. And I will agree...if you can keep the car under 150mph you will see better gas mileage. However, in traveling at a constant 75mph I have done 29mpg with 0 city driving.

 

"Don't exceed 3k in any gear" says to me stay at 3k but no higher.

But this whole discussion is silly anyway. The RX-8 is not a high gas mileage vehicle and it really should be run in a more spirited manner to reduce carbon buildup. Not to mention the fun that you buy a sportscar for.

 

6th for the Highway? sure but dont forget to shift around town. You can easily be in 6th at 40-45mph. If you ar serious about trying to get good mileage then you should be shifting to 6th all the time. In town when ever you are in a line of cars with no intention of passing- shift up to 5th or 6th. When you get a clear spot shift down for the power.

The gears are there for you to shift thru so use them. I bet many people getting 13 never shift above 3rd or 4th around town. whats the point of being in 3rd at 40mph if you are not going to be passing anyone on your way to that nexxt stop sign/light?

your right hand and right foot are a using a mechanical calculator. the output is power or mpg. the higher the gear and the lower the throttle the more mpg.

 

hahah 4mpg wtf, can barely drive 50 miles that way =(

i shift around 4k normal city driving, seem to be pretty decent.. of course... i don't quite do normal city driving anymore...