PhineasFellOff

I wanted to help clarify the gas mileage issue in a SIMPLE way by piecing together a handful of owners' data and focusing only on the "magic" hwy rating of 24 mpg.



RX8by: 25.1 mpg, 60 mph, 3000 rpm, Chicago, winter
Me: 23.6 mpg, 65-70 mph, 3250-3500 rpm, Los Angeles, winter
Zerobanger: 25-26 mpg, 70 mph, 3500 rpm, ??????, winter
Zerobanger: 30.2 mpg, 57 mph, under 3000 rpm, ??????, winter

Looking at Zerobanger's numbers as somewhat atypical, I think it's safe to conclude that the RX8 should be able to (1) slightly surpass 24 mpg if one drives at 65 mph and (2) surpass 25 mpg if one drives at 60 mph.



Although I think the mileage threads on this forum have provided invaluable information, I think the VARIETY of data and conditions can further confuse the mileage issue. I'm not by any means recommending that we stop those- any and all pieces of information are helpful- but I think if we added a mileage thread ONLY FOR drivers who follow CERTAIN CONDITIONS, more careful and simpler inferences can be made. The following are the conditions (in order of importance) to help us make better inferences:

1. ~300 mile NONSTOP trip done COMPLETELY on hwy done CLOSE TO COMPLETELY on cruise control at whatever speed (or rpm) you choose

2. provide information on geographical region and season (or month); if possible provide temperature but this is not critical

3. provide information on octane and gas brand

***** Edit: I'm adding the following three conditions in the appropriate overall order:

4. miles on odometer

5. month car was built (see sticker on the driver side doorsill; don't bother reporting VIN due to concern for privacy)

6. if DSC on/TCS on, DSC off/TCS on, or DSC off/TCS off (a handful of people believe having DSC and TCS off might lead to better mileage)

End Edit *****

As you can see, the requirements are quite simple. Obviously, not a lot of people will be able to contribute to such a thread, but that's actually desirable because things will remain less confusing. We only need a handful of contributors' data, which when combined with all the information from the other mileage threads, will allow us to make solid, meaningful inferences.

What do you guys think?

VikingDJ

I can't undersand for the life of me how and why these MPG discussions continue. Drive your car the way you want, get your MPG, and be happy. I think it's a foregone conclusion that if you manipulate your driving at 55-60mph, certain rx8s will reach beyond 25mpg. 25 mpg is definitely attainable on road trips, and hell maybe even 30 if you do enough manipulation and consume yourself with driving slow and saving gas. That is just not realistic and ideal, and it really serves no purpose or meaning. The real mpg of your car is how you drive on a regular basis. You can take any car and try this and get increases in MPG. I'm gonna call 25-26mpg very realistic on long highway commutes, and 30mpg possible under the most extreme manipulation of a long meaningless highway run. But hey, if you get 25-30mpg driving normally and no one believes you, that's their problem, not yours, so enjoy your mileage and give up on trying to prove it to the rest of us. Thanks!!

wakeech

hey now VDJ, if some people want to have their cake (save gas... and maybe the environment too, a little??), but eat it too sometimes (own an RX-8 and the fun incumbent in its purpose), then i suppose they ought to pursue that with as much effort as they choose.

boy oh boy, i'm always "in the zone" between 1.00 and 4.00am

PhineasFellOff

Viking, take it easy. At least allow me to explain why this might be important to you and me and everyone else. If we can get a good grip on what SPEED can get us 22 mpg, 23 mpg, 24 mpg, 25 mpg, 26 mpg, etc., then we can ascertain just how realistic that EPA hwy estimate is. We need HARD DATA from which to plot a graph. We can then compare the EPA rating to that for other cars. For example, I have an early 90's civic that has just about 260,000 miles that was originally rated at 36 hwy. Do you know what kind of mileage I'm getting PRESENTLY with that car? 33 to 38 mpg driving 70 to 75 mph. Can you fricking believe that?

See, I think that new "L" ECU reflash can in part be attributed to the muck raised by the people right here in this forum, from all the banter about bad mileage from the early days of this forum. Wouldn't you say that the "L" reflash is a positive result for the RX8?

The data doesn't care about the intentions of the person who provides it. One person is just curious. Another is pissed at Mazda. The data doesn't care. In the end, it can still benefit us all.

I think the next step is to fine-tune our data. Instead of just complaining in a general, chaotic manner (for example, "The mileage sucks"), we can pinpoint the mileage with "higher resolution" data. Instead of just complaining that the EPA rating is ridiculous, we can describe/characterize more fully the mileage, show EXACTLY HOW it is ridiculous.

And the method I'm suggesting above is a REAL SIMPLE way, much simpler and more uniform than the way we've been doing it in the various mileage threads so far.

Meowloud

I think this was a very helpful post for new people wanting info about the rex.
I too tire of the mileage threads, but if I had read this one when lurking before I bought my rex... then gas mileage would not have been one of my issues for not buying (the other was flooding, which I haven't done *knock on wood).

Thank you for your time and research.

Trx8

Here are two related threads that had a systematic approach to MPG:

RX-8 Discussion > Statistical Analysis Approach to Understanding MPG Issue
https://www.rx8club.com/showthread.p...threadid=13280

RX-8 Discussion > RESULTS: Statistical Analysis of MPG -- Long
https://www.rx8club.com/showthread.p...threadid=13404

This work was done by norton and analyzed data posted by members. The analysis didn't focus on high MPG, but did attempt to find what the dominant factors were and assign weights to them.

Last I heard, norton didn't own an RX-8 but was considering buying one. He had a 42 mile commute, and this was one of his conclusions after doing the analyses linked above:

Wepox

I am a RX-8 wannabe, I have been poring over the data on MPG and the Snow handling issues all along. I always appreciate the stricter guidlines to present data because I can judge the effects on the information.
I would assume that if a driver followed the strict guidlines to get a specific MPG that others achieved, that driver could reasonably assume that his 8 has another issue that is impacting the cars performance.

The other issue is the attitude of a select few that if they have been here all along and have seen it all then there is no reason to bring it up again. This is crap. There are newbies coming online everyday with questions and concerns that are not answered by reading through literally thousands of posts. Cut us all a break and lighten up on the rhetoric.

VikingDJ

I just love how all these conversations continue, yet absolutely nothing is ever gained by them. Yet I am finding myself reading this meaningless mumbo jumbo and getting annoyed at it. Don't you people realize you are trying to turn this car into something it isn't? Anyway, have fun and enjoy yourselves, if yapping about MPG is your idea of fun.

Trx8

I once asked my Calculus professor if he got tired of teaching the same class over and over. He promptly replied that he doesn't teach the same class over and over, there are always new students in the classroom. Hence he was teaching an endless supply of students Calculus, and they even had a book, with other reference books -- darn with all that material students still had questions and wanted to think about old things in new ways. I can't imagine the prof saying -- gees this has all been covered before, its in the books, there is just nothing to be gained here.

In reality not everyone is a professor, and even the profs get tired of teaching a topic to yet another group of new students. So, they shouldn't teach at all, or they shouldn't teach that class for a while, but I don't think its fair to say the new students can't take the class, can't ask questions, or can't question the conventional wisdom.

The idea of having a more friendly way of greeting and educating potential RX-8 buyers surfaces frequently, but the newbie-intolerance doesn't seem to be subsiding.

Yes people shouldn't register and ask "whats the deal with MPG", but since the information isn't on the surface, many will continue to walk-into-the-trap. The typical questions are:
- MPG
- Flooding
- Winter driving
- Car cost and option questions
- Performance
- Comparison with other cars

Shouldn't summary information and thread links for common topics be so visible that newbies can't help but find them? Then if someone does post a question that falls within this newbie area, rather than flame them, the proper response is to point them to the newbie thread.

mjd

I do think this is a good post. I've had my car for three weeks now, and I have kept track of the gas mileage for the last two tanks now. First, I got 19.2 mpg and the next one I got 19.7 mpg. This is doing from 55-75 with 90% highway driving. The first tank was 93 octane and the second was 89 octane. This has been pretty much driving granny style (all shifts at about 3000 rpms) My main gripe with the car is that doing 90% highway driving and not "pushing" the car at all I feel I should be at that 23-26 range and not between 19-20. I do understand that your gas mileage will depend a lot on how your driving style is. Seeing as how most people will agree with that, I have this question for everyone...I'm not exactly sure how to word it, but don't you think the gas mileage you get with the 8 might be a little more "sensitive" to how you drive than most other cars? With my last car, I could take it easy or drive the hell out of it with not much variance in mpg. Is it simply the rotary thats causing the havoc?

Nubo

It sure seems that way. For one thing, it absolutely gorges itself at idle. The other part I think is that it is SO easy to over-drive the car. Most cars will give a lot of cues, some subtle some not-so subtle, that it's time to shift and you really have to be in a performance mindset to rev up past say, 4000 rpm. In many cars at that point you've eaten up a good part of the tachometer (if there is one). With the RX-8 the power is smooth all the way to the stratosphere. When I'm on the freeway, not only do I sometimes forget to shift out of 5th, sometimes I forget I'm still in 4th! You can keep it around 5-6K without a sweat. The driving reality of the 8 is sort of the inverse of other cars. It's keeping the shiftpoint below 3000 that causes aesthetic pain :D

Xyntax

I just found out that I have been 3 mpg because I was using the windshield defogger the whole time. It turns on A/C without indicating it. Really, I'm serious.

Trx8

According to the manual on page 6-8. if the air is directed at:
- Window alone
- Window and feet
Then the A/C and fresh air mode will be automatically selected.

I try to avoid any Window (defog) modes and usually drive with air to dashboard and feet.

My driving is mostly urban/rural/expressway and I try to avoid city driving. My hunch is these things have a negative on gas mileage:
- Rev over 3750 during acceleration
- Rapid acceleration followed by brakes
- Miles driven while the engine is warming up
- Idle time, sitting at stop lights, warmup time, etc
I usually shift before 3500 and try to glide to stops. My daily commute is 6 miles each way. A few times per tank the car gets a good run of spirited driving. Lately I am getting 19.X MPG and am content with it.

PhineasFellOff

I'm very familiar with those two threads. Norton looked at what factors affect mileage. He took in a LOT of factors, in which respondents differed greatly. Variation is exactly what Norton wanted in his statistical analysis.

The analysis I'm proposing here is quite different. I'm not worried about what factors affect mileage; instead, I just want to see what speeds will get what mileages. Instead of variation, I want to see consistency. The only thing that can be compared between what I propose and what Norton has done are the number of factors we're looking at, respectively. Mine is considering much, much fewer factors, which will greatly simplfiy the inferences we make.

PhineasFellOff

I agree completely. This is exactly why I'm proposing this. You not only see what mileages others are able to get, but you also see what SPEEDS can get those mileages. Next, you follow the same conditions and see if you can match whatever speeds with whatever mileages.

Another outcome will be that we will know how realistic is the EPA hwy rating of 24 mpg. Again, what I'm proposing here will look ONLY at the EPA hwy rating, which is much simpler to evaluate than the city rating with its constantly changing conditions.

I feel that the dissenters aren't quite understanding what the analysis I'm proposing can do. We can very quickly and simply get a hand on what speeds will get what mileages, which is something that has NOT been done before in this forum.

PhineasFellOff

I'm not certaiin but my hunch is that the rotary varies more in mileage than a piston engine during CITY DRIVING ONLY. The rotary seems fairly consistent during hwy driving.

Again, I'm not at all certain.

PhineasFellOff

You think the "L" reflash is nothing?

Urchin

I wish my 8 would get 35 mpg and still perform like ti does, but it does not. Mileage is not why it has been winning so many comparison tests.

On my last road trip I tried for mileage and started driving at 70 mph. My wife kept asking why I was drivign so slow, so I slowely statred to speed up. She quit asking at 93 mph. Drove 250 miles in 60 degree weather at 85-95 mph and got 20 mpg. The extra $2.50 in gas I spent on gas by not driving at <60 mph was well wotth it. Enjoy the car while we can get gas.

PhineasFellOff

At the end of March, I am going on a trip practically across the US. I will have plenty of chances to gauge my mileage at 60 and 65 mph. I know it'll be agonizing, but WE NEED THE DATA. I can't wait to post my data at the end of March when I'm back from the trip.

blue flash

i have had my 8 now for about 45days and when i bought it the dealer told me you are buying a sports car not a compact that will get you 30-40mpg .so yes i do fill up with gas twice a week but thats my choice .i wanted the 8 and dont complain about the mpg zoooooom zoooooom

Trx8

Yes, I understood you are in the high-MPG regime, and those will be good results to see. I referenced norton's work because its related and may help others understand the relationshipe between city/highway and driving style ... his dominant factors.

I will be particular interested in seeing if you get results just above and just below 3750 where I think the 2nd injector kicks in.

PhineasFellOff

Well, I'm definitely going to test at 60 mph (3000 rpm), 65 mph (3250 rpm), and 70 mph (3500 rpm). The 60 mph will be excruciating, so I might test that one on only one or two tanks. I'll spend most tank "legs" at 65 and 70 mph.

Now that you mention it, it would be interesting to see what mileage I can get JUST above 3750 rpm. Maybe I'll try that on one tankful.

VikingDJ

I call this TRYING TO TURN THE RX8 INTO SOMETHING IT'S NOT. This would be like someone buying a LAMBORGHINI, and seeing if they can obtain more than 15mpg. I understand that many of you have to get this out of your system for whatever reason, but I do hope for your sake that you get over the MPG thing, and accept this car for what it is: A SPORTS CAR THAT IS NOT MEANT TO GET GOOD MPG. Have fun!!

Trx8

Since its his car, I think the way PhineasFellOff tests and analyzes his car is his choice. I don't see him trying to "turn it anything", he wants to learn more about how driving affects MPG.

When I had snow on the roads, I spent time trying to learn how snow affects performance. Although I wouldn't expect someone from non-snow country to care about those snow-driving threads. I also wouldn't expect others to criticize that I was posting related information. I would think that when someone realizes the thread was about something they didn't care about, they would just move on to a different thread.

VikingDJ

I guess I see this as an attempt to make the rx8 a good gas mileage car, as opposed to just doing it for your own fun and recreational purposes. Whatever the reason, you are right, I need to bite my tounge and ignore. My apologies.