My service rep at the dealer once said that RX8 fuel mixture is leanest above 4,500 rpm so I would get better mileage if I drive the car at the higher rpm. But this will only make sense when you are in 6th gear. I did notice that I get better gas mileage driving near 80mph than 60mh, on the highway of course. Near 60mph just around 3,000 rpm and 80mph over 4,000. This makes sense. So, when I get pulled over doing 85, I am telling the police officer that I was trying to save money on gas.

 

I don't believe the rx-8 would be streamlined enough to be more fuel efficient at 85 mph than 60.

I also do not believe that worrying about injector staging is a factor since the vehicle doesn't suddenly start dumping fuel and getting rich AFR's at a specific rpm as injectors are activated. It injects what fuel is necessary for the air ingested.

 

I am only stating what the service rep told me and what I observed. So far, my observation based on my driving and what the rep told me are consistent. I commute 80 miles per day mostly on highways. The days I drive faster, averaging over 80mph, I use less gas. What can I say?

 

buy a scangauge2 or some other tool that has instant readout, and I bet you'll find it not to be a valid statement.

 

 

Please don't get me started, this is the wrong place for that....

 

I havent found this consistently, but not to long ago, I was quite suprised to do 200 km at 145km/h average in 6th gear, with windows closed and air set to the top vents (means A/C is slightly on) and I used up less gas than I usually do in 100km.

I thought maybe the gauge was stuck or something, but even as I finished the gas tank, I actually did do more mileage on that tank.

I didint understand why, but that could be it.

I havent found this to be true at 120-130km/h that I usualy commute at.

Maybe I need to be doing 145km/h all the time haha

 

Neutral going down hills=]

 

Pure highway driving, particularly with the two entries at 25mpg. Those two had the fewest stops (pee breaks). All driving was between 70 and 80 mph.

I'm using Jeff's 4AT maps.

Common denominators:

1. Constant speed / minimal reving 70-80 mph
2. Nonstop (full to empty) driving -- the longer you cruise, the better mpg.
3. MM AP

 

the 4AT gets the best mileage due to the longer gearings.

 

I really don't see the relevance of that as it applies to my benchmarks being that I'm in the low 3k RPM range at 70+ mph. Highway speed is fairly constant unless I'm misinterpeting the definition of "longer gearings". I understand if more ports are being used, but given prior input it sounds like it doesn't really apply at the lower rpms... but what do I know.... I am still fairly new, but learning quick

FWIW, I believe MM has gotten his in the 350 mile range and he's modded like no other.

 

That's exactly what I was saying.

 

I've gotten 26/27 mpg at a very consistent 65 mph highway/Interstate with a little bit of stop & go on my stock MT. It's boring so I don't do it very often.

 

It's not speed, it's RPM. I drive the car hard, as it was meant to be, and over the last three years I typically averaged about 180 miles on a tankful before the low fuel light came on, 80% in-town driving, 20% freeway. In June, with gas approaching $5 a gallon in Los Angeles, I experimented with a few tankfuls when I would shift as often as possible before the secondaries opened at 3750 RPM, or just as the needle was flying past 3500, give or take. Mind you, while it was awkard rowing through the gears 2-3 times more than usual, and feeling more like my wife's Mazda3, my range immediately rose to 220 miles before the low fuel fight came on, an increase of 40 miles / 22%. I never bought the 8 for its economy and fully understood the trade-offs that came with such a unique, high-perfomance engine, yet it does show, if needed/wanted, you can indeed increase range rather dramatically.

Also, for the record, I switched from premium to regular over a year ago with no impact whatsoever to mileage or performance. I've got 48K miles on the car, service it by-the-book and have incurred no major issues since new.

 

I ran regular no-lead for two tank fulls when I first got my car (used 8k miles) and noticed knocking / rough idle. I haven't ran less than 91 since.