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18 MPG in the city!

Old 02-20-2004, 10:55 AM
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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.
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Old 02-20-2004, 10:58 AM
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well crap.. i drive like an idiot so I'll never get good mileage :b
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Old 02-20-2004, 10:58 AM
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But that is like actually eating only 1 lays potato chip! Almost impossible
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Old 02-20-2004, 11:05 AM
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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
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Old 02-20-2004, 11:18 AM
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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

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Old 02-20-2004, 11:20 AM
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Gotta stay below 65 MPH.
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Old 02-20-2004, 11:23 AM
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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).

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Old 02-20-2004, 11:44 AM
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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.
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Old 02-20-2004, 11:46 AM
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I've done that, but I contantly get 15mpg. Sucks. Driving wild, gets me 14mpg... so you know how I drive now huh?
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Old 02-20-2004, 12:01 PM
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Re: 18 MPG in the city!

Originally posted by Omicron
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.
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.
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Old 02-20-2004, 12:12 PM
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Originally posted by dag
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
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.
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Old 02-20-2004, 12:45 PM
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Re: Re: 18 MPG in the city!

Originally posted by zerobanger
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.
You and me both

Still haven't matched your 30mpg, yet, but I'll get there someday!
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Old 02-20-2004, 12:54 PM
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Re: Re: Re: 18 MPG in the city!

Originally posted by Elara
You and me both

Still haven't matched your 30mpg, yet, but I'll get there someday!
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.
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Old 02-20-2004, 01:02 PM
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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.
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Old 02-20-2004, 01:03 PM
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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
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Old 02-20-2004, 01:36 PM
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Zerobanger, what speed did you have the cruise control set at when you got 30 MPG?
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Old 02-20-2004, 02:16 PM
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Originally posted by LTAGFERN
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'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
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Old 02-20-2004, 02:35 PM
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Originally posted by GeorgeH
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.
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.
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Old 02-20-2004, 03:38 PM
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Originally posted by Omicron
Zerobanger, what speed did you have the cruise control set at when you got 30 MPG?
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.
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Old 02-20-2004, 03:40 PM
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Re: 18 MPG in the city!

Originally posted by Omicron
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.
: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!
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Old 02-20-2004, 05:22 PM
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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.
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Old 02-20-2004, 05:52 PM
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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?
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Old 02-20-2004, 06:24 PM
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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
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Old 02-20-2004, 06:50 PM
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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.
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Old 02-20-2004, 07:10 PM
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Originally posted by BlueThunder
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?
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.
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