Ok im really tired of my 8 being a gas guzzler
 

Ok so 2 months ago I got my 04 rx8 with 80000km from a dealer. Bought extended warranty. I also bought new plugs, coils, wires, K&N drop in filter, cleaned MAF sensor and reset e-shaft with the 20 brake pedal trick. All that was done at 81000km.

Now I gave it some time that maybe the ECU needs to relearn fuel trims. But this is completely ridiculous im doing 300km per full to the top gas tank. I got 320km once and I was like woahhh.

Thats 185 miles per tank for you americans. My daily drive is 1km to the highway and 24km on the highway once I hit work. 5 days a week. I am not an agressive driver, I redline once or twice a day if not im always in the 3500rpm while cruising.

Im pretty sure there is def something wrong with the car. Any ideas? I mean 20L/100km is not anything near what mazda advertised. The car now has 83500km.

Im pretty sure the car was never seafoamed, would that be a solution? or improve mileage?

My leading plugs were black with brown crust around the tips and the trailing were the same but less black and more brown.

What could be wrong? I knew when I got the 8 it would be around 12-15L/100km not freakn 20.

What kind of fuel are you using?

I get about 230 a tank, maybe more if I drive extra conservatively.

But get a compression test done, your engine may be biting the dust?
idk

Same for me, I have a 2005 and I can easily do 400km from a full tank, and thats with very aggressive driving.

You definately have something wrong. Check your compression, maybe a seafoam wouldn't hurt.

i always fill up petro canada super 94 with tecron or shell 91 when i cant get to a petro canada.

hey PGROTHE if you know how to seafoam would you mind giving me a hand? ill compensate you for your troubles.

Could be a bad catalytic converter also...

I usually get 250 to a full tank on premium with average driving in the city

Buy the Cobb Access Port...

If you get it from MM you can get a better tune than the one they provide from cobb...

Retune the car to increase your MPG...its running pig rich from the factory for cat protection...

I have an 2004 with about 160K on it and do very similar type driving routine an a weekly basis. I regularly see ~350k to the low fuel light 400-430km to a fill up of 55 litres. Best mileage was 600k to a tank full on a long cruising drive. SeaFoam couldn't hurt but I don"t see it making the sort of changes you are looking for. Somethings up.

Hey there,
I live in Canada and my 8 just passed the ol' 90,000km marker. I cannot get more than 340km out of a tank, from full to when the light comes on. When the light does come on though, there is usually another 10 litres of gas left. This is ULTRA conservative driving. No heat, coasting to stops, 91, or 93 octane gas. The few guys I have talked to around here with 8's all have almost the exact same milage. The guys that are getting 400 and over amaze me, congratulations. I've also found that even when i drive half way agressive with rev matching and daily redlines, I will still get almost the same milage, mabye 5km less. I moniter my consumption pretty hardcore because I'm a student, I live on my own, and incredibly broke. :(

I'm sorry I have no experience with sea foam, I would be happy to help though.
I've seen some video on this site that could help you too; there is a DIY for this too.

You live in Canada!!! It's winter right now, your fuel consumption will increase 20-30%! I haven't been driving my RX-8 in the cold that much, but my Prius went from 42mpg to 35mpg simply because the weather dropped to the 15-25F range (-10 or so C)

I am in the same boat, when I bought the car I was told 18mpg in the city and up to 24mpg highway. I went snowboarding on Monday, and did 220 miles with a full tank on the highway. I used cruise control all the way avg 70mph = 14.6 mpg on the highway :scratchhe

While it is true that our car is a thirsty one i think that complaining about your averages is pretty much useless because they clearly show that there's something to be looked at.
Start with the usual maintenance routine (spark plugs, coils, wires, fuel pump, injectors if your mileage is high etc) given that your engine is still running strong.
Worn out coils or spark plugs often make the fuel consumption fly sky high, so does a bad catalytic converter.

I usually get ~17mpg city, ~22mpg highway, and my cat failed (banging away at it all day to get a midpipe on before a trip tomorrow), and my mileage plummeted to ~9mpg.

Cat is definitely a possibility.

theres nothing wrong with his car, and if there is, the mileage will only improve slightly. That is the regular mileage of a car, and for the people who say they are getting 600, i don't know. It just sounds unbelievable that someones car could do 2x better than most people?

Oh well

Entirely possible. My mileage was cut in half from cat failure, so fixing it will double my mileage.

I usually get 300-330 miles per tank (~13 gallon fillup) all highway, 260-280 with city/highway mix. My last 2 tanks have been 140 miles and 110 miles with cat failure.

Health of the the entire powertrain matters a hell of alot more in our cars than most.

Yup surprise me too
Visiting family with the wife, Scarborough to Wiarton with a couple day's of local travel and back, low fuel light came on at 530km, Filled up with 60 litres technically I could have gone about another 30 or so before it would have cut out, but you don't want to stretch it too far you know:). Pretty much secondary highways 80-90kph. Amazed the heck out of me too. I'd done a 500km trip before but even those are very,very rare.
On a side note that engine just got replaced as of yesterday, sorry to see it go (15900km) still running smooth (low compression) , I hope the new one is as good.

Highway driving is a totally different world. I thought his original post was 1 km highway and 24 regular...owell

I believe the 04s were a bit more thirsty than than the years after.. But try cruising at 3k rpm. That about 40mph in 6th.

His first post says:

1km to the highway (city) and then 24 highway.

Meant to say winter will decrease your fuel consumption by 20-30%

your car is fine. thats about what im getting. just deal with it

I'd contend that your car is not in peak health either then.

Don't judge "fine" as being equal to your car, when better is clearly possible. True, he has the option of just "dealing with it", as you are, but he also has the option of working on it to restore the health of his 8.