Ok so I just did new coils, plugs, and magnecore wires.

My first plugs were fouled, black as hell, changed them at 28k.

With the new plugs and everything I am still getting around 14mpg. This is with my shifting being at or slightly before 3k rpm.

What is a good way to tell what flash I have?

 

^ What type of driving do you do...city or hw?

 

I think the sooner you accept that you aren't driving a Toyota Prius the quicker you will fathom that the RX-8 will never get good gas mileage. It doesn't matter what you do you will max only increase it by a mile or two if you are lucky. I get 4-5 KM a Litre if I am lucky (which usually I am a unlucky guy)

 

YAY! yet another mpg thread. /end sarcasm
Do you drive mostly street? How agressive would you say your driving is? (lots of redlines?)

I've gotten as low as 11mpg on a tank, but combined with some freeway miles, I average 17.8

 

I've never computed the gas mileage on my '8. I can't handle the truth.

 

I get about 11. I laugh at my gas bills.

Gotta pay to play.

 

^

+1

 

You want MPG? get a car with 1JZ engine that gives you about 100 hp.

 

Short trips should be the only reason your plugs are black. They are very bad on engines, not burning off the rich gas and not burning off water(condensation) in your engine. Your plugs should not be black. Have you changed your Air Filter and cleaned your MAF sensor yet.

 

I wouldn't rip on him too bad, its not like he said it and isn't trying to do anything about it. I doubt he is asking for 25 prolly just around 18ish. If I just payed to change all that I would be pissed that nothing changed.

(Unless it is all city then I can see that number easily being true)

Also, try calling Mazda give them your VIN and ask what flash has been done, they should be able to tell you.

Also I would shift after 3K so your not putting to much strain on the engine, that also hurts mileage)

 

The MAF is clean. The filter was done about 5k miles ago and looks great.

Im not looking for 30mpg, around 17 would be nice.

Most of my driving is in the city.

As far as how I drive it, I dont redline it much, take off slow from the line shift at around 2800 - 3000 rpms until about 4th gear then I just skip 5th and stick it into 6th.

 

The worst I've ever got is 18, and that is usually this time of year when the temps are low and the car idles high. I normally get 20 mpg, probably 70% highway. That is with 2 different engines, didn't change at all. On a long trip I actually got 27 mpg, cruising about 75 mph on the interstate without stopping in between.

I generally shift around 4k then I open it up about once per trip. If you are shifting that low, I don't think there should be a 4-6mpg difference.

For me to get 14 mpg, I think I would have to redline it at every shift... Hmmm

 

I had around 13 my last tank

 

Also regarding the short trips comment.

I always let my car idle in the garage to warm up to where the temp gauge usually rests before it even moves out of the garage. Same thing when leaving work in the afternoon, I sit and wait for it to warm up.

But I can tell you when letting it warm up my whole garage smells like gas every morning.

 

I've been getting 15-16mpg and shift points seem to make very little difference, but I'm 70%c/30%h. The few times I've spent a while on the highway it gets to just above 20mpg.

 

Thats the problem right there. Cars use alot of fuel sitting at idle, not just ours, but EVERY car. Since you aren't moving that is basically just fuel being wasted. Just let it warm until the temperature needle moves, then you can take off. You don't have to wait for it to be fully warmed (needle in center). Just drive it like normal and it will warm up fine. This should get you at least a couple more MPG.

 

Ok well Ill give that a try. I always did that to make sure the oil is moving and it makes sense to me that it would create less wear with it being warmed up.

 

mamma mia !!!!! I predict a marked imrovement when you stop this misinformed proceedure .
Your car warms up much quicker when you drive it (than sitting there like that) which is way better for it as well .
Start it - wait about 30 seconds , put it into gear and drive , slowly at first . Then wait a good few minutes after needle hits normal before canning it like you stole it .
Also - minimise short trips , these kill gas mileage . If you just need to pop down to the store - take a more economical car to do this .
And - premix has shown to help with gas mileage .

 

when I was in Houston last summer, I went from averaging 20-22 MPG in South Carolina to about 14-16 MPG in Houston. A friend of mine at the Health Science Center I worked at experienced a huge drop in gas mileage in her Saturn. She called GM because she thought her car was broken and they informed her it was the gas used in TX. I think, at least in Houston, they added up to 10% ethanol in the gas. So that may play a huge role. not sure if it would cause that much of a drop though.

 

wee..... here we go agin!

 

How about you sell the 8 and buy a miata? I think you will be pleasantly surprised in the difference in the mileage.

 

Paying for the gas isnt and issue I was just expecting some improvement. Oh well.

 

This may be why your plugs were black. The rotary really does need to be wound out on a regular basis. Doesn't mean you have to drive Fast and Furious everywhere you go, but do wind it out here and there. Have you ever heard the beep when your rpms get towards 9000? You need to hear that beep regularly. It wastes a little gas for a few seconds, but you'll get it back from a smoother engine.

Yeah, the warmup thing will drink gas. This car really drinks gas at idle; I can see the needle moving!

The final part is city driving. Stop and go is not this car's forte. I proved it to myself last summer, when road improvements removed a bottleneck from my homebound commute. My mileage immediately improved by 4 miles per gallon.

 

I would say I hear the beep at least once a day.