On saturday coming home from Reno (220 miles) using cruise control at 3500 RPM I averaged 25.3 MPG. This was with the first 40-50 miles being in terrible snow and ice. The rest of the drive was very relaxed with good driving conditions. I think I would have got 27+ had it not been for the first 40 miles.

In the city I get 17-19 depending on how hard I drive it.

 

Im interested in the build date theory, but I think the reason the west coast may get worse gas mileage is because we have alot of hills to climb.

 

thx

and i dont know. lord know whats going to happen if i figure out how to post a pic or make an avitar.

beers

 

https://www.rx8club.com/showthread.p...re+Vin+and+MPG

searay i figured it out, just cut and paste the address window into the thread.

beers

 

It shouldn't be idling rough. How bad is it? Is the whole car shaking or do you feel it in the shifter only? If you feel it throughout the car I would definitely take it in for service! It could be fouled plugs or a vacuum line problem! check all your lines and connections around the air intake tube! Or it could be the dreaded engine failure that a few people experienced with similar problems (rough idle. poor mpg) as yours. I'm not trying to scare you and hopefully it's and easy fix, but you should bring it for srevice immediately,good luck!

 

Build date on mine is 05-03. I bought it 12-19-03. Only 750 miles so far but filled up today - 9.9 gallons at 159 miles. All of it city driving (and we got hills too in East TN). And I don't baby it either. Lots of short trips (5 miles or less). Longest drive yet probably about 50 miles.

 

10 mpg is abnormal and you should pester your dealer. I generally get 16-18mpg under normal circumstances and the lowest I've got (following the breakin) is about 13 and that was over 100 miles of *very* hard driving. I find it difficult to believe they can claim 10mpg is normal while holding a straight face... My car is a June 2003 build date .. vin is 019xx

 

Let's just say this, while sitting at a traffic light, etc., idling, I won't rest my head on the head rest 'cause of the vibration. It started out just in the shifter...which I think is normal, but now, things inside the door rattle, the seats shake...etc., but only at 800 rpm idle speed.

 

Nope, that's not normal. Take it in for service ASAP!

 

Not that I'm bitching about poor gas mileage or anything......anybody who has done that on this forum just gets on my nerves. GO BUY A TOYOTA PRIUS OR SOMETHING if you are pissed about the poor fuel economy!

My 8 is averaging about 16-19 MPG with about a 50/50 mix of city highway driving. It is not driven hard because I'm usually always right behind somebody.

My old 1991 RX-7 convertible with 95,000 miles on it gets about the same MPG as the 8 does, and it weighs MUCH more than the 8 does. I feel that Mazda did a pretty good job with the Renesis when it comes to the amount of power gained from its design over the old rotary while maintaining the fuel economy.

 

Except that 10MPG is not just bad gas mileage being complained about, it's abnormal and likely indicates something wrong with the car. As such the owner should complain (but not to us) about it and pressure the dealer to diagnose and fix the issue, or replace the car. It could be something as boring as a bad thermosensor keeping the engine running in an enriched mode cause it thinks it cold all the time.

Folks getting 10MPG consistently should not just moan about bad mileage and do nothing about it - it just proliferates the gloom/doom of rotary=bad mileage - I mean hey, the car does get low mileage but not that bad.

Simon.

 

Will,
Your 800 RPM idle speed seems low to me. Mine idles at 1,000 when warm. You say that it smooths out if you give it just a little pedal which probably puts it near 900-1,000 RPM. Has it always idled at 800 RPM (even before this started)? Almost sounds like a loose vacuum line, or something getting jiggled loose when checking the oil, fouled spark plugs, etc.
Smelling gas in the garage after shutdown is a definite no-no with some serious potential for unpleasant consequences with all the hot parts.
Low idle speed will have a definite impact on fuel mileage as well. Plus, you are probably having to fiddle with the gas pedal to keep vibration down, and then over-rev starting from a stop to keep from killing it. Any of these will degrade fuel economy. All of them combined will really impact it. I would definitely go back to dealer. If they give you the same song and dance, then find another dealer or call Mazda customer service.

 

Dude! Did I strike a nerve???

That's exactly the point...thanks Simon. I will check for loose hoses, etc. Who knows?

 

Exactly! Esp. the over-revving when starting from a stop. It always luggs wants to die. Quite frustrating...but what's even more frustrating is convencing the dealer service dept. to do something about it without confrontation.

 

I have a new 2004 RX8 I didn't caculate the first tank but did do the second. I filled it up and at 202 miles I filled it up again, it took 12.37 gallons which is 16.33 miles per gallon. I drive it pretty hard and all has been in town no highway miles. I also park it in the garage and there are no gas smells. I will be going on a 400 mile trip to Florida and will keep you posted as I collect the data.


2004 Winning blue RX8

 

Will,
Take it to the dealer and have him ride with you (not just talk to you) to show him what it's doing. Stop before you get back and have him drive it back to dealership with you in the car. This will either convince him there is a problem, or help identify anything you might be doing to bring it on. I doubt you are doing anything to cause it idle rough, but sounds like the dealer needs an attitude adjustment and sometimes you just have to demand their attention in order to get it.

 

My values :
13.2 MPG in city center (17.8 l/100km for european readers)
24.5 MPG outside city (9.6 l/100km)

 

What Will Barger is saying about the dealers is correct. Mine told me they are "still on a learning curve with this animal". At least he is honest. My wife was getting 10 mpg in town and maybe 15 on highway. She is a "granny driver". I complained to the dealer and he did the following.
Replaced the plugs with the hotter ones. This eliminated the "ticking noise" and engine vibration at start ups.
He then spent the next 3 hours with the portable phone in his ear and under the hood & inside the car whild Mazda walked him through Re-flashing or Re-programming whatever part it was. It took multiple tries before it was done. The result is now almost 15mpg city and 19 hwy. She usually drives 75mph on the highway so I can live with that. We have very different driving styles so I never see the milage she is getting but it did increasewith my driving style too .