18 MPG in the city!
 

I've been trying an experiment this week. As the RX-8 only uses 1 set of fuel injectors from 0-3750 RPM, I have driven way (too) sedately all week, deliberately shifting at or below 3700 RPM.

The end result? 213.6 city miles traveled, 11.792 gallons used = 18.11 MPG! :D

So FYI: Driving style, and most especially shift points, seems to make a major difference in mileage.

well crap.. i drive like an idiot so I'll never get good mileage :b

But that is like actually eating only 1 lays potato chip! Almost impossible :)

Yes, I agree, and was just going to come back and add that it was REEEEEEALLY difficult to drive the car like this. Drove me abso-freakin-lutely NUTS to do it. This car was meant to be revved! I did however get kinda used to it by the end of the week.

I look at it this way: If the car gets 15 MPG instead of 18 MPG on my weekly commute, I use 1.21 more gallons weekly. Since gas prices around here are running about $1.65 a gallon, this means I spend about $2 more a week on gas if I drive the car like I love to.

Is $2 more a week worth it? HELL YES!!! :D

I do tons of highway driving (2K miles in 20 days) and I've been trying to figure out how to keep the RPM's below 3750 on the highway to get good gas mileage.:p

dag

Gotta stay below 65 MPH. :(

Yeah I know. I was just wondering what if Mazda set the gears up so that 6th gear wouldn't hit 3700 RPM until 80MPH instead of 60. I would love to see the gas mileage I would get then (since most highways traffic easily cruises at 70-80).

dag

Omicron I did the same experiment on my current tank. Usually get 125-130 miles by the half way mark. Been shifting before 3500 rpm and only occasionally topping 4000 rpm. I got 150 miles at the half way mark. A 20% increase in efficiency! My conclusion is that revving does affect your consumption badly.
Last night I started having withdrawal symptoms. So I drove like a mad man.

I've done that, but I contantly get 15mpg. Sucks. Driving wild, gets me 14mpg... so you know how I drive now huh?

Re: 18 MPG in the city!
 

I have tried and tried and tried to tell everyone this. Infact, when I posted my 30.22 MPG over a 95 Mile trip I got flamed to hell and back. I got that gas mileage keeping the revs to 2900 rpm on cruise control.

Keeping them to 3200-3300 RPM on cruise control over a 220 mile trip I got 26 MPG.

And last, on my weekly commute I get 19-21 in my rx-8.

When I drive it like I stole it I get about 17.

To do this Mazda would have to change the final drive ratio, wich would effectively increase all gears, and the final result would be a noticible reduction in acceleration at all speeds - your RX-8 would feel like a pig.

Or, they could just install a super steep 6th gear, which would make the 5-6 shift very wide (i.e., a large reduction in rpm), and 6th gear would be complely unresponsive to the throttle below 100 mph or so.

Re: Re: 18 MPG in the city!
 

You and me both :)

Still haven't matched your 30mpg, yet, but I'll get there someday!

Re: Re: Re: 18 MPG in the city!
 

Elara...

I have yet to match it either. That day with the 26 MPG was the following week. It was during the same trip. The difference was there was a ton of snow for the first 50 miles, so I was driving eraddic. If it wasn't for that I think I would have maintained 28 for the entire 220 miles.

26 is not bad, but again, I was driving like a granny, surely not fun.

In response to GeorgeH (a few posts back) . . . perhaps Mazda could add a 7th gear (a 'highway / cruise gear') so 80 MPH in 7th would be around 3400 RPM. Although I'm not certain right now, seems as though when I'm traveling 80 MPH in 6th the tach reads 4000 RPM.

I will post and let you know how the PCM/ECU re-flash comes out. I just took my car in for the passenger air bag recall and they are going to re-flash my ECU. In the meantime here is the e-mail I received from Mazda regarding the issue.

Dear Tim,

Thank you for contacting Mazda North American Operations. I appreciate the opportunity to respond to you.

You are requesting current campaign information regarding your 2004 Mazda RX-8. Our records indicate that your vehicle, with Vehicle Identification Number (VIN) JM1FE173940116546, is affected by RECALL# 1604B, Front Passenger Side Airbag. The necessary repairs for this campaign can be completed free of charge to you by an authorized Mazda dealer. A campaign letter is not necessary to have this campaign completed at a dealership. Once the repair/inspection is completed, the Mazda dealer will update our records to indicate that it has been completed. As you noted that yuo are already planning to have your vehicle in for unrelated services, you may wish to have this completed during that trip.

In regards to "flashing the PCM", simply have your vehicle inspected for any concern that you are experiencing. If it is then determined that your vehicle requires this procedure, then it will be performed. Naturally, each dealership has full and unlimited to all technical information, like technical bulletins. In fact, technical bulletins are pieces of literature specifically designed for use only by a Mazda technician.

Please understand that this office is not in a position to diagnose or instruct on repair procedures for your RX-8. We could not speculate if your vehicle For these matters, Mazda relies on the factory-trained technicians at authorized Mazda dealerships to diagnose and repair concerns that may arise with a Mazda vehicle.

Each Mazda dealership has access to Mazda's Quality Assurance
Department via a technical hotline. This is offered to each dealership should they need assistance from Mazda with diagnosing or repairing a Mazda vehicle. Therefore, simply have your vehicle inspected...your dealership will perform any services that are neccessary...including the "PCM flash" as determined relevant.

Again, thank you for contacting Mazda. It has been my pleasure to assist you. Please feel free to reply to this message with any further questions or comments.

Please take a moment to give us your opinion about our e-mail service. Click the link below to complete a brief, online survey.

http://www.zoomerang.com/survey.zgi?...09GH3CPK39V6BD

Regards,

William Zdan
Specialist, Customer Assistance E-Business




Original Message Follows:
------------------------


Form Message

Email Address:
First Name: Tim
Last Name:
Title: Mr.
Message Address:
Message City: Spokane
Message State: WA
Message Zip:
Work Phone:
Home Phone:
Subject1: Ownership & Maintenance
Subject2: Recalls & Special Service Programs
Current Mazda Owner: true
Model: RX-8
Year: 2004
VIN: JM1FE1739401

Message Body: I am taking my car in to have the e-brake handle
replaced under warranty. While I was there I wanted to get the PCM or ECU reflashed. I know that there is a TSB to get this done and I wanted to make sure that I could get it done. I have poor gas mileage and when the car is warm I am experiencing the rough idle. If this is available I want it done. I am tired of getting such poor gas mileage.
Thank you,

Tim

Zerobanger, what speed did you have the cruise control set at when you got 30 MPG?

I've herard that 7 speeds are on the automotive horizon (I think it was BMW or D-C) but that the only way it was going to happen was via an automatic - 7 gears apparently is just too many for a manual - people just don't like shifting that much.

Me? I think about dropping the gears 5% - it would help acceleration, and 6th gear seems like overkill to me - at least from a crusing noise standpoint (i.e. 5th is only marginally noiser than 6th). Of course, now I realize that 6th does afford mileage gains, if you keep the speeds down.

George

I think part of the problem is that a 7-speed shifting pattern is kind of strange. 6-speeds is perfect. To shift into 1st and 2nd, you move to the left and shift. To shift into 3rd and 4th, you let the shifter fall into it's natural position and shift. To shift to 5th and 6th, you push it to the right and shift into gear. The shifter feel would have to be very intuitive in order to make this possible, otherwise you'd be finding yourself in all kinds of different gears, especially when you were new to the car.

for starters I was trying to prove the EPA's mileage was accurate, that it was possible to get the 24 thay they claim. I drove like a granny between 57-60 mph which was from 2900-3100 rpm. When I needed to slow down instead of hitting the breaks I would do it with the decel on the cruise button, and speeding up the same thing.

It wasn't practicle and I dont drive like that normally. With my FD when I drive the same trip I get about 25 MPG, but thats at 80 MPH cause at 80 in 5th i'm only at 3000 RPM.

Re: 18 MPG in the city!
 

:D Omicron, that is excellent considering the cold climate you have up there. I just made the switch from 91 to 87 octane during the last few tankfulls and my mpg went up to 17 mpg from 15 mpg. This is strictly city stoplight to stoplight driving and I drive on the moderate side, 4000 to 6000 rpm shifts are common and the occasional 8500 rpm shift. Your right though, this car ought to be driven like it was intended with very high rpm shifts in mind, if not what's the point of having it!

i've been driving like this for quite a while now, after i saw the posts on this forum, (it was probably yours zerobanger). I always get over 20+mpg since then. driving like a maniac, i used to get like 15. Not to surprising results i figured.
and driving like this isn't too hard, just obey the speed limit. nobody is impressed with you driving 90mph on freeway, i know lots of jalopies that do the same. besides, when i cruise at 65mp, cars actually slow down to admire my car.

RX8bliss. what you mean by this: "I just made the switch from 91 to 87 octane during the last few tankfulls and my mpg went up to 17 mpg from 15 mpg." I thought that we supposed to use premium in the RX8. Maybe this is explain my 14mpg in city. I thing I'm going to try the regular. However, what this damage or effect the engine perfomance in any way?

I just got the reflash on Monday, and I may wish I hadn't. The car doesn't feel as quick as it did before, especially in the 3-6000RPM range. It also used to have a noticable kick when the tertiary ports opened, almost like a turbo. Now I barely notice it - I feel a much more linear and constant pull from 0-60. As for mileage, I'll wait for the next tank to check. So far, it appears to be unchanged (I was getting 18-20 prior to reflash).

I was afraid this might happen - maybe I can have them back-rev me and I'll just live with my CEL :)

There's no need for a 7 speed trans. A two speed/overdrive diferential is all that's needed. All the trans ratios stay the same so you keep the normal performance, just hit overdrive in 5th or 6th and get great highway mileage.

Had this a couple of decades ago in a Fiat 124 Spyder.

that wasn't me bro, reread my post right above. and i always use 91 oct. makes me feel like a big man *ahem* though i hear 89 is ok to use, for me 91 just feels better.

According to:
http://www.mazdausa.com/MusaWeb/disp...ehicleCode=RX8

The Auto and Manual have different gear ratios:
- Auto, 4th gear, 0.694
- Manual, 6th gear, 0.843

I think my AT is below 3750 at most expressway speeds.
<edit>
I checked twice recently, 80 MPH is about 3350 RPM
(1.5 needle widths over 3250 RPM)
<edit>

Is the 3750 RPM cut-on the same for ATs?

Re: Re: 18 MPG in the city!
 

Wow, I admire your self restraint! :)

Hmmm, don't know if I can STAND driving like a granny for another week! ;) Perhaps week after next I'll try the 87 octane, and drive like a granny, to see if I can get 20 MPG in the city. Hmmm.



As for the gear ratios, I think a tall 6th gear is the best solution for highway economy. Just tall enough that 80 MPH would be turning the engine at 3500 RPM. That'd be ok in my book - I don't mind downshifting to pass!

Mazda, are you listening? :D

I just did my first fill up today.

233.6 miles / 12.214 gallons = 19.126 MPG

This is still in break in with moderate driving under 6000 RPM. I've been trying to shift around 3500-4000 RPM on average. I'm assuming the first tank from the dealer was 91 octane. I'm using 93 octane from my local Exxon.

That's pretty good - I did an extended trip last night from San Diego to Burbank and back again - lots of freeway cruising (but not at 60mph, more like 82-85) and got 20.7mpg which is about the best I see. With my normal driving style I see around 17-18mpg. If I'm having fun, I've seen 15mpg. So yes driving style, shift points, how fast you accellerate from speed A to speed B etc. seem to have dramatic effects on mpg. Although I still think there's a small number of people who actually have some kind of car problem where they get horrible mileage regardless of their driving habit... I wonder if any of them have checked their intake for oil? I could imagine an oily MAF could really hose things up.

I think if you are driving for nothing but gas mileage that's great, but also realize that you probably foul you plugs up quicker than those who use the whole power band.

Driving at 3,750 rpm in a 6-speed, which gets 19.4 mph/1,000 rpm, = 72.75 mpg. 88.125 in my AT, which gets 23.5/1,000.

BTW, I'm almost always way under 3,750 in the city, and still get around 15 mpg in my early-VIN car. The dealer says the ECU is properly set, and offers no other solution.

There is another thread on 87 octane that is more in depth but I gave the 87 a try and it resulted in a 2 mpg increase with my same moderate driving style. Now how this will hold up is another story but the car seems to run and idle a bit smoother. I guess 87 octane is fine for a stock car and normal to moderate driving in mind, but for aggressive driving (redline) and performance mods, I would definitely stick with 91 octane.

I have the auto trans(medical reasons). At 3000 rpms my speed is 73mph. It is hard to keep the revs down but I have never got lower then 20mpg on the 8. This is my 7th rotary since '71 and its more fun then any other.

just blasted out my best tank yet. 22.8 with the ac running.

fla in the winter sucks. most of the tank was run with shifting from 1st to 3rd to 5th 6th. all before 3.5krpms.

then running the interstate at below 3750rpm. i think the next tires are going to be taller. so i can run 80mph at less than 3750rpm.

tank before 18.8 with tcs and dsc tests and two top speed runs. 138mph. but the area i test in is short.

love this car.

beers

UGH that explains the RX8 I was stuck behind in traffic last week... The guy was going 50 on the highway. I pulled up next to him trying to encourage him to either drive the speed limit or trade his Silver 8 in for a Mazda 3. :)

Then I downshifted into 4th and screamed ahead of him... he did not follow. Oh well.

OK, I don't know much about tuning and piggy back units, but could the point at which the second set of fuel injectors kick in be changed with either of these two options? In my naivety I believe that the kick in point could be “moved down” to increase performance or “moved up” or removed all together to increase gas mileage.

Can anyone tell me if this would be possible? It would see an in cockpit setting for this could be very useful …

I think you have a good idea. Why not have a switch for max hp,gas mileage and lower hp(when you loan it to someone that might not have the need or experiance)..... to handel it.

What is the right acceleration rate for stop and go city driving?

I have a 6 mile drive to work with 4 stop signs and 4 stop lights. I start out gentle because the car is cold, but about 1/3 of the way into the drive the temperature needle is moving pretty good.

I would guess that hitting the 2nd injector at 3750 RPM for "city stop and go" won't get me the best MPG, and may not be the best for car, and best for the car is also an issue.

In granny mode I could keep it around 2000 RPM or less, but that almost feels like the car is out of its power range, and I am wondering if the mid-2000s or higher might actually improve the MPG.

To get the best MPG, what is the best RPM range for frequent city acceleration from a full stop?

Mazda outlined in the book when to shift, its something like 14 MPH in first gear, I forget the rest. I found that shifting at 3000 RPM yields enough power for day to day driving and will get you the best gas mileage.

you get 90 pct of your torque by 3000, so its enough for day to day.

I've been saying this for I don't know how frikkin long that if you keep the rev's down you can get 19mpg like I do.

...besides, I'd rather drive slowly - its easier to pick up the chicks when your not flying by them :D .

zerobanger --

Thanks, I will try accelerating from a stop such that it shifts before 3000.

Yeah, but it's SO hard to do! :D

ugh- I've been shifting low and holding my rpms to 2500 for the past two days- at 120 miles I was still 2 notches above halfway, in ALL city driving, BUT....I couldn't take it anymore. On my way to the gym this evening I gave up on the experiment and drove like a banshee.

I also found out that keeping the rev below 3500 rpm has improved my consumption drastically. I had 150 miles on the clock at the halfway mark, my best ever. Like Elara, after a few days my right foot started itching and I went cuckoo.

Hope I can make it longer...

I finally broke the 20 mpg barrier with my last tank. Of course, it was 98% highway driving with the cruise control set to 72-75 varrying depending upon what traffic was like. I got a 20.45 mpg on 87 octane.

Since 1/10/04 I have had this car and have not done a large percentage of highway driving alone on a tank of gas. Even this was not a good measurement because at least 45 miles was done on a two lane road where I averaged around 60 with slower periods going through small communities. Most times in town here I get around 13 - 14 mpg.

This tank full I am keeping it under 3500 rpm and will see what driving like a granma feels like. As others have said trying this method, it was very hard to do today and almost to the point of being painful.

I did find out that in 6th gear at 3500 rpms it is going 70 mph. So, this will be ineresting to see if it does what others have said.

And furthermore I do NOT plan on driving like this very often after this experiment, unless I start getting tickets, God forbid, but I did buy the Velocity Red... :)

Sorry for quoting old entries in an old thread; but I was wondering if the anyone figured out how to get a 6th gear with a ratio closer to the top ratio used by the Auto transmission. I am given to understand that the top gear in the 2007+ auto is even a bit taller than the one from the 2004-2006 models (though i could be misinformed).

Does anyone know if the other markets where the RX-8 is sold have the same gearing as us? If not, do they have a taller or shorter 6th gear? I find the jump from 1-2, 2-3, 3-4, and 4-5 just fine for me; but I find the jump from 5-6 much too close for my liking, so I'd ideally like 6th gear to be a bit taller.

Coming back to the topic, I find that even if I drive with revs limited to 3000 in the city, I find that it only is viable in Spring and Autumn, as the AC, especially in dense and jammed traffic can and in at least one case did eat more fuel in a half mile than a 40+ highway trip (results I observed just two months ago, so this was not hypothetical but actual observation). I am planning to get a Scangauge II so I can better fine-tune my shift points as well.

I have been shifting much quicker keeping my RPM's down in South Florida traffic. I have also been taking it out of gear when coasting. I have not kept track of my mileage but notice my gauge is not dropping as qucikly as before. That is in traffic. I still exercise my baby on certain roads I driive on daily and do redline at least once a day. I guess it is a mediation of sorts and still enjoy what I bought this car for.

2004 thread. Kinda cool to look back at gas prices

On my last road trip I got 27mpg. I wasn't using cruise control, doing a fair bit of lane changing, and averaged 80mph. I left it in 6th most of the way.

My last stint of city-only driving saw me at 20mpg.

Driving it the way it's supposed to be driven usually nets me closer to 16-17mpg.

'07, build date 10/06, 6700 miles as of the day of this post.