I don't want to hear about how your mpg sucks or how you can supposedly change it. I want to hear from people who have had an MPG problem with their 8 and actually fixed it. Driving another car does not count.

 

What kind of "problem" are you talking about?

The 8 has crap mileage as a feature, it's not a problem

Not if you're getting < 10mpg, that's a problem.

 

i get 17-18 mpg and its no problem

 

i get 17 intown 20-23 highway just have k@N drop in

 

I get about 15-17mpg and commute about 300miles a week. so much fun lol

 

does it help?

 

sounds better and a tiny better mpg

 

well im getting about 13 and would like to get about 16. it would make it so I would drive my car more than ride my motorcycle. im thinking about changing coils, plugs wire, air filter, and get the new Ecu flash. Ill let you guys know how it turns out.

 

move out of the city. mpg will go up..

it is that simple.. btw, if you are on the interstate and it is moving at 5mph.. you are in the city..

it is that simple.. now my mpg dropped to 19mpg.. changed the fuel pump and plugs.. reset the room fuse. back to 21 mpg..


beers

 

I have started a long term project to find out how to get more mpg out of an 8 without changing the spirit of the car. I plan on doing simple mods that we can all do in our driveway and recording the results of the mpg change. I am new to the car and new to the rotary, so if anyone has any suggestions or mpg results from mods that they have performed in the past let me know. I figure there is a small portion of the RX-8 community that would like better mpg out of their cars, I have an online store as well and plan to sell the parts I use in the project.

I have created a web page on my site dedicated to the project, there is some info on there now but I will be updating it consistently as the modifications are performed.

Check out the page and let me know what you think, if there are any suggestions you can use the contact us form at the bottom and it will go directly to me:

 

It's all in the way you drive. The car is EPA rated at 16 mpg city.

 

I agree, I can see that already in the short time I've had the car. But do you think that adding a free flowing exhaust, ignition upgrades, and intake would yield better mileage? It's worth a shot. I have read other articles where the addition of a drop in Green filter to an RX-8 was worth 5 hp on the dyno, I want to know what it does for mpg as well as hp.

At least we will know what the effects of the mods are if there is no improvement in mpg. That will satisfy my knowledge at least, plus I like to know how the parts I sell perform so I can have a better understanding of exactly what they do or don't do. This way I can not sell the stuff that does not work.

 

Agreed. The thread title is misleading; it suggests that all 8's have a "problem" with their mileage (i.e. getting less mileage than they're supposed to). The thread "How can I get better MPG?" is a better way to express it.

No big deal, but I suspect titles like this contribute to the erroneous perception of the 8 as a "problem car." Like "has anyone found a way to stop their 8 from drinking oil?" or "which engine are you on?" (the RX-8 equivalent of going up to someone at a party and asking—so that everyone could hear—if they had stopped beating their wife.)

 

Good point. In the big picture this car does not get outright horrible mileage compared to many cars on the road. Look at trucks for instance, they are all over here in Florida. Big ones, medium ones, small ones, all getting worse gas mileage then us in 8's. I think some people were not aware of the mileage of the car when they bought it, or were mislead by some salesman, which provokes the "problem" response. The only "problem" is the gas prices, I'd pay more to have this car regardless, I would have bought a Mazda 3 or similar car if I wanted good mpg. I am one that is interested in seeing if I can get better mpg's out of the car though, but none of the mods I want to do is going to negatively effect that spirit of the car. Most of the stuff I am going to do has already been done, I am just going to see what it does for mpg as well as HP.

 

I have an AEM cai intake, BHR Ignition Coil system, SR catless mid pipe, Mazdaspeed cat back exhaust, Cobb Accessport. And I get 13 to 17 around town and 21 on the freeway.
And if I turn the Nitrous on I get 10mpg.
As you can see these items did nothing for my mileage.
Mazda's intake and exhaust system are very free flowing and quite capable of letting the engine breath more than necessary.
If you want to document these change per item on a dyno I would like to see that.

 

This is a great project, John. I love my 8, and if there are farily simple things we can do to save gas, all the better.

Dave

 

john,

welcome.

i have done all the na mods you can do.. non have changed the mileage one way or another.

but please do try, you never know what you can learn.

btw, harmony. is that on 192 between st cloud and melborne?

beers

 

Have you tried positioning a brick (or something comparable) directly UNDERNEATH the gas pedal?

 

as someone with a lead foot I do know of a way to get better mielage .
- a flash that leans up the mixture under load will do it .

used to get around 330km/tank around town but that rose to 360km with a decent tune that reduced afrs to about 13 vs 11 stock .

 

Thanks! I am looking forward to learning more about the RX-8 and it seems the members of this forum know quite a bit. I can tell you anything about a Miata, as we are SCCA Spec Miata road racers, but the magic spinning triangles are new to me. Don't hesitate to correct me or offer advice because of that reason.

Harmony is on 192 between St. Cloud and Melbourne, in the middle of nowhere just where I like it, but not all that far away from civilization. We are not a brick and mortar store, so traffic is not a concern to us as this is our home office.


About the NA mods, what mods have you done and using what parts? I am trying to see what people have done already so I do not use the same things, such as a Mazdaspeed cat back when it is proven not to do anything. If it is alright with everyone on here I will list the suggestions on my sites project page and sort of provide a database of things that might work. You can email me using my sites "contact us" form on the bottom of every page. Just tell me what parts you have tried, wanted to try, heard worked, or have researched already and I will list them with your names and website link/forum profile/car pics.

I am planning on doing some things that people probably will not think of doing normally or have not tried yet, simple things such as using lightweight oil in the tranny and rear end to reduce parasitic drag on the rotating parts and maybe a long way out having the bearings dry lubed by Boca Bearing (ceramic bearings) to decrease rolling resistance. Adjusting tire pressure might even do something. I will report what works and what does not work too, so we know what not to do. Each part has to do a little, whether it works or not combined together they should result in some sort of gain or loss, either way it is an experiment, and experiments do not always work. It will also help me to know what parts might work on other cars too, as I think the mpg mods will be gaining popularity in the near future and it might be good to sell these things. Research is learning, and as a parts seller/racer knowledge is potential sales or speed.

 

I'm thinking there is something wrong with my mpg, I am getting around 20mpg in the city with an 04 MT, oh yeah in winter in Canada on top of that. Original coils as well.

Using Lucas UCL as premix, use 6th gear as much as possible, no short trips. Still redline at WOT almost every drive.

 

I hate to keep referring to Spec Miata, but that is my expertise (and at least it is a fellow Mazda). Air/Fuel ratio mods are something that yields huge (to a stock Miata) gains on our Spec Miatas, I am sure they would have the same effect on any car, as the more gas that is used above the ideal AFR is wasted. The Spec Miata racers have figured out through countess hours of dyno time what the ideal air/fuel ratio is to make the most power on those motors, it is a little richer than the stoich (14.7 to 1) ratio because we are pulling in more air and getting rid of the exhaust easier, so more fuel is acceptable to correct the ratio. We just have to adjust the air flow meter manually in 90-93 1.6L cars to change the ratio, pretty much just lying to the computer. This of course is not possible in a mass air metered car without doing a reflash.

I can't help but think that with adding an intake and exhaust, pulling in more air and exhausting it easier, a flash would be needed to remap the fuel mixture and correct the difference (if the cpu does not do it automatically). I am not sure, that's where you guys come in. Is it necessary to reflash the cpu after intake and exhaust mods to realize the full benefit?

Brettus,
Did you lose power when you had the cpu flashed? And, where did you get in flashed at or what product are you using to flash it yourself? That is definitely a mpg increase, was it in addition to any intake/exhaust mods?

Thanks,

 

Sounds like you are way above the average according to what I have read so far. We average the same here in Florida, with half of the miles being highway. Could the premix be helping to increase the mpg?

 

Aside from the normal stuff (not sitting idling, keep off the lead foot) keeping your plugs changed is about all I have seen that makes a difference. I put a drop in K&N air filter and it may have increased the mpg some, but not enough to quantify. On long trips with 90%+ freeway driving I have come very close to 25 mpg, but my normal route back and forth to school on winding roads gives me around 20 normally.

I have gotten consistently better fuel economy with each new flash from Mazda (bought in 04), started out getting around 18 mpg and a little better each time, and from what I understand some of the flashes did lean out the mixture. Of course you can get too lean, even quicker if you have a catalytic converter. Overall I'm satisfied with my fuel economy since it beats what the EPA sticker says, but I know that is not true for most drivers and even most cars other than the RX-8.

 

When was the last new flash released from Mazda? I have an 07, surely there was one in between then and now. Also, has anyone had any experience with aftermarket flashes, like Racing Beat?

So far it doesn't sound like there is a lot that will improve the mileage on these cars, so it is a good challenge at least. It will be interesting to see what happens. I am looking forward to the simple easy things like lighter oil in the tranny and rear end, some cheap things might do the trick and it sounds like not many people have done it yet.

Thanks for all of the input, keep it coming.