BillK

Why are you using 5th at all?

For maximum gas mileage, just think "as soon as I get to speed, shift into 6th." You also should probably shift 1->3->6.

For example, on a normal street, you can usually start in 1, shift into 3rd and be cruising in 6th any time you are going faster than around 35 MPH...

8_wannabe

I tried this for awhile and the car is so not fun driving this way, I shoulda got a Metro. Besides which there was no detectable improvement to gas mileage. I finally decided, "if I wanted a three speed then why did I buy a six-speed?" and went back to my normal, fun driving techniques. As I did that and total mileage increased, my mpg started going up. I don't think this driving technique helps, it strips away all fun from the '8, and I'm still trying to unlearn the habits gained while doing it. IMHO!

msrecant

I agree with you 100%. Driving technique may get you 1 or 2 mpg but kills the driving fun. Beyond that my mpg problem is 7 or 8 mpg anyway. Best to drive normally and wait until you get 2,000 or 3,000 miles on the car before dealing with this issue.

8_wannabe

One other question for someone more knowledgeable than I. Someone said before the ECU "learns" your driving habits when it's new and adjusts accordingly. So, if you are following these screwball techniques is the car also learning bad habits? And if so, when you revert to some normal driving techniques wouldn't this put the ECU all miscalibrated for "normal" driving? Just wondering, but it seems like you might be making things worse doing this.

silver8

Here's a question: I often do a lot of short trips, 20 minutes or less, and when I do, I can watch the gas gauge move. Yesterday, I actually made a couple longer trips, 40 miles one direction, a two minute stop and 75 miles in the opposite direction. On the longer trip with the car all warmed up and averaging close to 85 MPG with sprints to triple-digits through Camp Pendleton (for those who know SoCal), the gas gauge barely moved. Of course, when I did fill up before my return trip I still got less than 16 MPG....thank goodness for those long highway trips at the end of the tank though or I might have had my worst mileage ever!

Oh, so back to my question. Many people citing their mileage have talked about the highway/city mix of driving, I am wondering if those getting higher mileage aren't also driving a warmed-up car (independent of whether it's city or highway)?

Care to comment?

P.S. Canzoomer, you mentioned "hoping" to get better mileage...does that imply you are keeping the car?

silver8

Here's a question: I often do a lot of short trips, 20 minutes or less, and when I do, I can watch the gas gauge move. Yesterday, I actually made a couple longer trips, 40 miles one direction, a two minute stop and 75 miles in the opposite direction. On the longer trip with the car all warmed up and averaging close to 85 MPG with sprints to triple-digits through Camp Pendleton (for those who know SoCal), the gas gauge barely moved. Of course, when I did fill up before my return trip I still got less than 16 MPG....thank goodness for those long highway trips at the end of the tank though or I might have had my worst mileage ever!

Oh, so back to my question. Many people citing their mileage have talked about the highway/city mix of driving, I am wondering if those getting higher mileage aren't also driving a warmed-up car (independent of whether it's city or highway)?

Care to comment?

P.S. Canzoomer, you mentioned "hoping" to get better mileage...does that imply you are keeping the car?

canzoomer

Well, if you read in the Canadian section threads, you will see I am involved in an engine computer, ECU over-ride project..

If this pans out as decent I will then be keeping my car..

It finally reached the point where I decided I am willing to spend some of my money to fund the project, find the people with the resurces to do it, etc..

Talk is cheap. Until I have results to show, it is all speculation.
I may have to return the car before finishing, but I know others who are keeping theirs and who are willing to help, so even if I return it I may buy another afterwards.

I was offered a GT6 with roof and NAV yesterday at MSRP with no roof or NAV..

Things are getting better..

silver8

Canz: in fact, while sitting on a conference call here I looked at the Canadien Dyno thread and saw your input there, so I do see your efforts. Good redemption on your part (not that you needed it!).

I got my title in the mail two days ago. I am strongly considering returning the car, but haven't identified exactly what I would replace it with. I am running out of time though. Having traded in my last car on the 8, I need something. Mazda, your efforts or someone elses may well address the shortcomings, but I won't be in a position, should I take the buy-back offer, to wait that out. If I get another car, it will be with the goal of keeping it 4 to 6 years. If there were a late-model M3 I could get for under US$40K, I could well be set for that 4 to 6 years. Though, I haven't found many priced at that point and even if I do, that represents an $8K premium over the 8. You can buy a lot of gas for 8K!

Good luck in your efforts, I will keep an eye out...whether I keep the 8 or not.

canzoomer

I am still looking at the options too.
I have a TT lined up, but the guy has to find his new car, and of course i have to get the cheque from Mazda.

Looked at the Acura CL Type S coupe with 6 speed yesterday.
http://www.acura.ca/AcuraEng/Models/CL/Specifications

I can get one for exactly what I would get back from Mazda for my 8.

Nice car. Nicely appointed.
Lots of power and features.
Bit heavier (1592kg/3500 lbs)

And it is built by Honda. I have had VERY good experiences with Honda cars and delaers. Parts prices and aftermarket are inexpensive and well provisioned.

Still, if the RX-8 can be fixed, I will probably keep it..

And if not, well, I am still liking the TT, but can only afford a 2 year old one with warranty extensions.
If I want new, then the Acura is pretty attractive..

As for the gas, let's do some math:
As I am buying premium 91 octane now for $.84 per litre, and at around 16l/100 versus 11l/100 it is costing me an extra 5l/100 at $0.84, and if I drive 15,000 kilomteres a year:
5 l x 15000/100 = 750 liters
750 @ $.84 = $630 per year.
So, over 3 years I would be paying an extra $1,890 for gas as compared to the TT or Acura.

Not a HUGE number, but it adds up.
Enough to pay for extras, like accessories and car toys..
Plus with the RX-8 I am about to have to drop around $1800 on wheels and winter tires.
Neither of the other 2 need that. The Acura comes with all weather radials, and the TT with spare wheels, winter tires and Quattro.

So, over 3 years the price for keeping my RX-8 is about an extra $3,700
And if I pay for mods to make the power and maybe some mileage about $2000, although i will get a bit of that back on gas savings..

Hmmm, arithmatic. I like donuts better..

commentator

Well canzoomer has taken a lot of heat on this forum and I appreciate his comments good or bad. I have sent in my papers to return the car. I don't think this issue is going to be resolved before the deadline but there is always another one out there if it is. I just hit 1400 miles on mine and got 13.2 mpg on my last tank of 89 octane. No I am not a lead foot. As I have said before there is too much disparity in MPG users are getting to be chalked up to lead feet or break in theories. I sure hope these issues are resolved, I would like to consider buying another 8 later.

silver8

[QUOTE]Originally posted by canzoomer
[Not a HUGE number, but it adds up.

I agree. I came up with (and posted elsewhere) a similar number (around US$600 per year) comparing the 8 to a 330 based on 13,000 miles per year. The other calculation I added to that post (too lazy to go find it) was the time spent thinking about and/or actually getting the gas. It's a little early in the morning for heavy calculus, but looking at your numbers, I would guess your tank capacity at about 48 litres, based solely on your 16l/100 and my getting about 200 miles between fillups. That means that at 15K klicks per year, you are going to the gas station 50 friggin' times per year!

Why couldn't Mazda at least engineer the car with a bigger gas tank? I would be that most cars averaging 15 MPG have at least 20 gallon tanks.

canzoomer

Last tank i did a highway run, but paid attention to keeping rpm below 4000. This is 126kmh in 6th.

I got around 13.4l/100km or 17.6mpg
I looked in the RX-8 book tonight, and found the first intake switch happens at 3750 where it goes from 2 to 4 runner.
I bet that if one kept below 3750 one could easily hit 20mpg.

Of course that is 115kmh (71mph)

Booooorrrring!!

BillK

2004 Audi S4 - rated MPG 15/21, gas tank 17.3 gallons.

That means if you fill up at 1/2 tank you get to fill up every 130 miles or so.

Sound familiar?

mikeb

Yes, it sounds too familiar

khoney

I wish the gearing in 6th was such that we could go up to 80 without the intake switch. Typical highway speed where I live is about 75. I'll bet we would see some better MPG numbers from a lot of people.

poison123

""2004 Audi S4 - rated MPG 15/21, gas tank 17.3 gallons.

That means if you fill up at 1/2 tank you get to fill up every 130 miles or so.

Sound familiar?""

Ah doesn't the Audi have over 300HP also? A little bit of a difference I think.

astrlsrfr

I am awaiting a copy of the California "title printout" from the leinholder so that I can send all of the paperwork in on the buyback.

Meantime, at 1800 miles, here's what I am seeing wrt MPG:

Certainly NO IMPROVEMENT WHATSOEVER. if anything, its getting worse. My 8 rarely does better than 13ish MPG; last tank was 12ish MPG. I use the "ish" convention because I don't have my notepad in front of me, and besides, it really doesn't matter, considering the despicable fuel economy levels I am seeing.

My opinions of the RX-8 remain unchanged: Its a solid car, built with precision engineering & high quality. The handling is top-notch. However, something has gone HORRIBLY wrong with the ECU tuning, and unfortunately, Mazda remains hunkered down in silence. Many people still oogle & ask me about my car; When I tell them how bad the mileage is, they always recoil in horror. I am quite sure they won't be buyers & they will slowly spread the word. GOOD. Maybe Mazda will eventually get the point that they HAVE TO ADDRESS THIS PROBLEM or their sales will suffer.

mikeb

I dont know if you reed this thread but a lot of people started getting better mileage at 2000 and your at 1800

canzoomer

Yes, some do. And some don't.
For example I managed to get better mileage on a tank recently, by driving very carefully always below 4,000rpm.
And even then I got around 18mpg.
I have 3600km on the car ( that's 2,236miles for Americans)

BillK

The original poster simply said "most cars that get 15 MPG have over 20 gallon tanks." The 2004 S4, regardless of its HP, shows that even some newer cars don't.

silver8

I would bet a Toyota Prius has as much oomph as the 8 does if you keep the latter below 4K. In fact, it seems incongruent to be so obsessed with maximizing mileage in a sporting car. Now, I have read articles about people trying to get the best possible mileage out of a Prius or the Honda Hybrid, but that is a completely different sort of car.

Yes, I think I am submitting my paperwork tomorrow. I just hope I can find a used M3 at an acceptable price. I am still a little resistant to spending that kind of dough on a car, but my wife is doing her all to talk me in to it...what's a guy supposed to do?

ptiemann

With my previous car (Firebird) it was much worse. Someone explained me that the fuel tank in the firebird is not cylinder or cubic shaped, but more like a triangle.

It's wider at the top than at the bottom.

The Firebird's display tells you how high the tank is filled. So if it was filled to half height, that meant you had 6 out of 16 Gallons.

Maybe it's similar with the RX-8.



My dealer gave me a first fill-up with the car and I got 17.3 MPG out of it. Turned out that they only have 87 Octane gas.

I drove mostly between 3500 and 4000 rpm, but a few times hitting 6000 rpm and once >8500 (I got to hear the beep)


If everyone measures exactly, maybe it has to do with how 'early' the model is? I got mine 9/16/, no idea when it was built. Can that be told from the VIN?

-Peter

Rotor_Newbie

woohoo.. i got 18.4mpg on the 8. Its only been my 5th tank. =-]

7Neverdies

Being my first post here, i think i should attempt to clear some things up.

I've owned 2 rotary vehicles and worked on many with friends. Gas mileage has never been a rotary strong point. If you bought the car for gas mileage.. you bought the wrong car.

Now my guess is Mazda richened up the fuel maps to over compensate for all the blown FD3S engines. Mazda/Ford doesn't want a repeat of the 3rd generation RX7. So, the loss of HP is happening because of richening up the maps. Guarantee, you lean it up, it will make more power but at the expense of engine life. Mazda is working hard to get the Rotary back on the streets, and I for one would like to see another RX7 in the near future.

My tip to you all, if you want better gas mileage is in fact to drive the car harder. I think that if you all bring the car up to 4500-5000rpms every shift that you will actually see better gas mileage. If you shift at 3k you are making the engine work harder, since its not in its torque band to lug your car down the street. Every Rotary i've owned i've always taken to 4.5K then shifted, i've always seen better gas mileage that way. Also note your throttle input, how much gas are you giving it? The faster you get the car up to speed, the less it has to work. It might seem counter-intuitive, but everything on rotaries is. If you don't agree, then don't, i'm basing what i know off of dealing with these cars for years.

I don't know for sure if Mazda has a "break-in" map for that car wired into the ECU? It might be running rich for the first 2000-3000 miles just to compensate for break-in.

When I rebuilt my FD's engine, we set the maps on the PFC extremely rich to eliminate any chance of detonation. If your car is having a lot of carbon deposits, its running too rich. Mazda should be able to reflash the ECU to fix that.

Anways, just my advice. I really like the RX8 after driving a local owner's. After i sell my 7, i plan to stick with the rotary and own an 8. Good luck to you all out there! Let me know if my advice helps any.

:D

shebam

Thanks for the practical perspective and advice. Good to hear, since I mailed in my "I'm keeping it" letter this morning. Never seriously in doubt despite the mpg angst.

As has been noted in another threat, carbon soot does collect at bottom tip of each exhaust. Seems consistent with your observation.

New wonder: will keeping the DSC/TC off, as has been put forward to increase performance and possibly help mileage, extend any "learning curve" or break-in period programmed into the ECU? Would help to have some electronic rather than observation data, but at this stage it would seem the only ones who have it are Mazda, and (being a lawyer) I can understand why they ain't saying. Maybe if folks started chatting this up with service depts. on their visits we can find out if they have been given a clue.