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-   -   12 MPG!!! Help!!! (https://www.rx8club.com/series-i-trouble-shooting-95/12-mpg-help-91329/)

Daylou93 06-02-2006 02:51 PM

I just filled it up again. I'm quite aware of your little 3rd grade equation. I went 197 miles and used up 15.2 gallons using an average of 12.96 MPG. I was previously stating a guesstimation of the MPG and gee...I was quite close wasn't I, CLEOENT. To the rest of you I very much appreciate your advice and I will try high revving it. Anyone think I should use a fuel injector cleaner on it? Not sure if that's alright with a rotary.

Razz1 06-02-2006 03:02 PM

You must be doing city driving and alot of warm up time and short trips.

It should be more like 16.7 MPG

I can get 22.5 MPG on all Hwy. All city driving and short trips kills your MPG.

Try going up a steep hill. If your car bogs and can not accelerate normaly the you have a clogged CAT. That will kill MPG. CAT is covered under warrenty.

416to212 06-02-2006 03:26 PM

I'm pretty new to this club and I am already sick of all the "Mileage" threads. I know I can just stop opening these links but I'm afraid I'm addicted to this board and I love hearing people whine about how life sucks.

If you can't afford gas why not buy a Honda or Toyota? I wonder if other sports car clubs and off-road truck clubs complain about mileage....

Daylou93 06-02-2006 03:40 PM

I'm not complaining about the car. It calls for 18 MPG city driving, 24 for hwy driving. I'm getting 13 so therefore there is something mechanically or electronically wrong with my car. I seek to correct that problem. That is all. I'm fine with it running the way it was designed to run.

therm8 06-02-2006 03:42 PM

How many short trips do you take per tank?

EyeBall Fixer...(o)(x) 06-02-2006 03:48 PM

Stop complaining, 12 - 16 mpg is normal for some 8's.
When you get 9 mpg like some of us you'll earn that right!
Besides, my knowledgeable service dept told me that 9 mpg is normal.
My bad mileage is due to grannying it, No wait! It's due to racing my AT
with bad gas...
They wouldn't lie to me... would they..!?!

Seriously...
Mazda doesn't have a clue why some 8's get poor mileage and others get 20+

It's easier to blame the customer for something they're doing wrong...

Daylou93 06-02-2006 03:50 PM

I do live in a small city, but it's surrounded by highways so it's a pretty even share of driving conditions. And as for short trips, probably the average is 15 min. considering in a city everything is pretty close including my job. I do give it at least 5 minutes before shutting it off as recommended.

Daylou93 06-02-2006 03:51 PM

Lol! Too true Eyeball! I think I have to agree with that. 9? Damn!

zoom44 06-02-2006 04:03 PM


Originally Posted by Daylou93
It calls for 18 MPG city driving, 24 for hwy driving. I'm getting 13 so therefore there is something mechanically or electronically wrong with my car.


not true- look at the sticker again. 18 is a median with 15 being possible driving like the test. your low may just indicate you are not driving like the test.

not saying you dont have an issue- just that your mpg doesnt automatically mean there is something wrong with the car

zoom44 06-02-2006 04:06 PM


Originally Posted by Daylou93
I do give it at least 5 minutes before shutting it off as recommended.


you let it sit at idle for 5 minutes every trip or close to it before shutting it off? does it sit that long running after start and before you start driving? theres your issue then

Daylou93 06-02-2006 04:19 PM

Lol! No, the manufacturer recommends to not run a rotary for less than 5 minutes at a time. And as I stated, I have tried driving it at lower RPMs to preserve the fuel. I have a degree in Automotive Technology, and I am a Service Adviser at a Mercedes, Audi, Porsche dealership. The mazda specialists are at a loss as well as me as to why I am getting such shitty MPG. It is below spec. I am just trying to see if maybe someone else had this problem as well and somehow corrected it. I don't believe the cat is bad because the o2 sensor is reading fine downstream. The air intake seems to be cleared and functioning properly. There is not any codes. The fuel trim is where it is suppose to be. Small things like the tire pressure are fine. I have tried to shift differently to see if that helped, but it didn't much. Air filter is fine, it is not due for a tune-up for another 10k miles and it recently had the routine service performed. I'm thinking maybe fuel injection cleaner, but I am not sure if that is safe for a rotary.

Skythe 06-02-2006 04:31 PM

Tis normal. You're lucky to be gettin 200. i'm more like 185.

What you are experiencing, sir, is not a problem but a feature.

whenson417 06-02-2006 04:35 PM

I read a thread in the last week or so where the guy (or girl) replaced their cat with a highflow one and got better gas mileage and better performance as a result. Before the swap they were getting some crappy mileage and the cup holder would boil water. I do not remember the particulars but I believe that they stated the O2 sensor was giving off normal readings before the swap. After the swap the cup holder was cool again and they got better mileage. Do a search to get the actual statements before you quote me on anything.

Napboy 06-02-2006 04:42 PM


Originally Posted by Skythe
Tis normal. You're lucky to be gettin 200. i'm more like 185.

What you are experiencing, sir, is not a problem but a feature.

it's not normal... i've had two rx8's and both got around the same mileage. about 240 per tank in the city and about 280 on the highway.

his mileage sucks and should not be accepted because a few others are experiencing the problem.

zoom44 06-02-2006 04:51 PM


Originally Posted by Daylou93
I have a degree in Automotive Technology, and I am a Service Adviser at a Mercedes, Audi, Porsche dealership. The mazda specialists are at a loss as well as me as to why I am getting such shitty MPG. It is below spec. I am just trying to see if maybe someone else had this problem as well and somehow corrected it. I don't believe the cat is bad because the o2 sensor is reading fine downstream.


well the degree could be your problem :D: i keed i keed

ok- do not believe that the cat is ok because the O2 sensor is reading fine and there isnt a code. i could link you to a whole slew of posts that had bad cats and no cel. it will eventually but only when the honeycomb breaks lose. and even then it might not. just recently had another one. a freind had an issue and after driving the car i and others said bad cat. of course his dealer said no CEL etc. he went to another dealer that dropped the cat and pieces fell out. pull the cat and physically look at it from both ends.

also pull your coils and look at the back. if there is evidence of melting or burning or the plate they sit on looks like there was arcing going on change the coils. pull the plugs and see if they are fouled. also check that you have the new style plugs and not the old style.

Skythe 06-02-2006 05:37 PM


Originally Posted by Napboy
it's not normal... i've had two rx8's and both got around the same mileage. about 240 per tank in the city and about 280 on the highway.

his mileage sucks and should not be accepted because a few others are experiencing the problem.

A few?

what would you consider to be normal for all city driving?

On what would you be basing your assessment?

tiltmode43 06-03-2006 02:03 AM


Originally Posted by Napboy
it's not normal... i've had two rx8's and both got around the same mileage. about 240 per tank in the city and about 280 on the highway.

his mileage sucks and should not be accepted because a few others are experiencing the problem.

Well, from what I experience, the longevity of each fuel tank is greatly effected by the amount of short trips. I drive to school, to/from lunch, and home form school every day. That is a ton of short trips and if I do not drive any highway in that time, and use up the whole tank, I get about 200mi or so. If I drive with highway included, the number can get up to around 240. I never realized how much the different kinds of trips could effect mileage before this car...

zoom44 06-03-2006 11:28 AM

thats exactly it- that extra trip around the block for lunch(really 2 starts adn 2 short trips) will kill the mileage especiall if they are not accompanied by a nice easy cruise on the freeway home(no stop and go just light throttle highest gear possible etc)

tiltmode43 06-03-2006 02:55 PM


Originally Posted by zoom44
thats exactly it- that extra trip around the block for lunch(really 2 starts adn 2 short trips) will kill the mileage especiall if they are not accompanied by a nice easy cruise on the freeway home(no stop and go just light throttle highest gear possible etc)

Heh, I'm not the one complaining though :)

mhl12 06-03-2006 03:58 PM

I've read somewhere that car companies test their cars' mpg basically on a treadmill so there's little air resistance and friction... in other words the most ideal conditions. So I would expect the mpg less than the advertised number.

10kRPMS 06-03-2006 04:19 PM

I also got 12-13mpg all the time I shifted at 6500rpms to 7500rpms

Daylou93 06-03-2006 06:34 PM

Thanks for the advice. I think I'll look into the cat issue first. And the plugs as well.

fisherdn 06-03-2006 06:47 PM

As some have mentioned the gas you put in can make a big difference. I just got back from a trip and got 22.9 mpg on 87 octane and got over 25 mpg on shell v power 93 octane more than once with almost the exact same driving conditions. My car obviously likes that specific kind of gas.

supergoat 06-03-2006 06:50 PM

200 miles on a tank? Same here.

However, I also have a 2nd car that gets 25mpg city and 30mpg highway that I can drive if I ever tire of spending $45 a week on gas. :)

Easy_E1 06-03-2006 06:54 PM

250ish per tank ,,mostly freeway at 4000 rpm


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