Fuel Economy Worse than Estimated! Please help!

[Anthony1410]

Hi I just purchased a new 2009 Mazda RX8 R3 edition. The vehicle still only has 1700 miles on it. Right now I'm averaging 12.5 mpg in mixed driving (city and highway). This is well below the estimated 16city 22 highway. Does anyone have any suggestions or advice? I would GREATLY appreciate it. I'd be delighted just to get it up to 19 for an average. I generally run the engine between 3k and 5k RPM, while occassionally reving over 7K to keep it clean. I warm up the engine before leaving and use 93 octane fuel. Is 12.5mpg normal? Thanks!

 

[evilmonkeyMSP]

rotaries FTW! lol

hopefully someone can give you some usable info

 

[martispeed]

Well I know that you are supposed to let it warm up and all but that’s probably why your MPG is less than advertised... I mean think about it how long are you letting it warm up? 10 min 15, 30... You are using fuel while it’s warming up and not going anywhere thus getting 0mpg every morning for a short period of time.

If you’re in a colder climate this will obviously have a greater affect since it will take longer to warm up.

 

[Anthony1410]

No i'm warming it up 3 minutes or 2 minutes, that's all

 

[Metallic36]

Yeah, definitely make sure you warm it up.. then rev it to around 6k or 7k before you turn it off. I flooded the one we had by simply turning it on, backing up five feet, and turning it off. Of course I didn't know anything about having to warm it up first until I read online about it. Next day it wouldn't start, had to take out the plugs and clean them, then put oil into the intake. Fun crap. We traded it in the next day after we got it running, too much maintenance crap for a car that would just be normal. You have to add oil occasionally too. But yeah, it had crappy gas milage, about as crappy as my F-150 truck.

 

[martispeed]

Ok well throw that theory out the window haha... Maybe someone else will chime in??

 

[Old Rotor]

Hi I just purchased a new 2009 Mazda RX8 R3 edition. The vehicle still only has 1700 miles on it. Right now I'm averaging 12.5 mpg in mixed driving (city and highway). This is well below the estimated 16city 22 highway. Does anyone have any suggestions or advice? I would GREATLY appreciate it. I'd be delighted just to get it up to 19 for an average. I generally run the engine between 3k and 5k RPM, while occassionally reving over 7K to keep it clean. I warm up the engine before leaving and use 93 octane fuel. Is 12.5mpg normal? Thanks!

Thirty seconds is fine for a warm up before you drive off then you drive easy till it's up to temp. I looked at the window sticker and read the small print....

Actual Mileage will vary with options, driving conditions, driving habits and vehicle's condition. Results reported to EPA indicate that the majority of vehicles with these estimates will achieve between 13 and 19 mpg in the city, and between 18 and 26 mpg on the highway.

 

[R-X-R]

Yeah, definitely make sure you warm it up.. then rev it to around 6k or 7k before you turn it off. I flooded the one we had by simply turning it on, backing up five feet, and turning it off. Of course I didn't know anything about having to warm it up first until I read online about it. Next day it wouldn't start, had to take out the plugs and clean them, then put oil into the intake. Fun crap. We traded it in the next day after we got it running, too much maintenance crap for a car that would just be normal. You have to add oil occasionally too. But yeah, it had crappy gas milage, about as crappy as my F-150 truck.

lol,.,its like having an insane baby.,.,

 

[Shadow102]

drive it until about 5k miles and have a complete record of your fuel economy. When you take it in for the first oil change at the dealer present them with your findings so they can look it all over.

 

[solidtrance]

12.5 is really low. I sometimes get mileage that low, but only when I am being really aggressive with the fun pedal. Even in the winter I manage to avg 15+. I agree about keeping very specific track of you fill ups for a while.

On another note revving to 7K will not keep the engine clean. The last set of valves doesn't open until 7250 and to get any benefit from that RPM you have to be at WOT (wide open throttle). Also the Tach reads 300-400 RPM high so 7000 indicated is more like 6600-6700. Run it unitll the big hand is on the nine. Loads more fun that way.

Check your oil level. Hope this all works out for you.

 

[jessedrifter]

12.5 is really low. I sometimes get mileage that low, but only when I am being really aggressive with the fun pedal. Even in the winter I manage to avg 15+. I agree about keeping very specific track of you fill ups for a while.

On another note revving to 7K will not keep the engine clean. The last set of valves doesn't open until 7250 and to get any benefit from that RPM you have to be at WOT (wide open throttle). Also the Tach reads 300-400 RPM high so 7000 indicated is more like 6600-6700. Run it unitll the big hand is on the nine. Loads more fun that way.

Check your oil level. Hope this all works out for you.

what he said. and if you still have questions visit rx8club.com they and search. they have alot of useful information

 

[DMRH]

Thirty seconds is fine for a warm up.

Good advise if you want to risk your engine with premature failure. Regardless of what Mazda advise (for marketing purposes), or what uneducated owners advise. The rotary engine still uses Aluminium rotor housings & cast side plates. These two dissimilair metals will always have different temp coefficient that cant alter the laws of physics nor so-called expert advice.

Time is always required to bring the slower expanding metal to temp & match the quicker expanding metals expansion limit.

Thats why I have always given my RX's at least 5-min from cold & driven slowly until everything is up-to-temp.

14lt/100km is a pretty normal consumption for an RX-8 in city driving. Your 19lt/100km is quite excessive but its expected the ECU willl run the engine rich until a run-in period is exceeded. Over time as more KM go into the engine you should settle down a little but its not hard to send the ECU to a Japanese company for a re-maping if the consumption fails to drop.

Knightsports re-mapped the ECU in my old RX-8 & I actually scored 10lt/100km in highway mode as well as extra power.

REgards

 

[altspace]

This will help you in regards to rotary engines, why they consume so much gas for such a little engine. It's not a flaw in the engineering, but rather part of the design. As with any motor design, there are positives and negatives. Unfortunately public response and misunderstanding is what "fuels" the negative.

http://www.mazdas247.com/forum/showthread.php?t=123695571

 

[Old Rotor]

Good advise if you want to risk your engine with premature failure. Regardless of what Mazda advise (for marketing purposes), or what uneducated owners advise. The rotary engine still uses Aluminium rotor housings & cast side plates. These two dissimilair metals will always have different temp coefficient that cant alter the laws of physics nor so-called expert advice.

Time is always required to bring the slower expanding metal to temp & match the quicker expanding metals expansion limit.

Thats why I have always given my RX's at least 5-min from cold & driven slowly until everything is up-to-temp.

14lt/100km is a pretty normal consumption for an RX-8 in city driving. Your 19lt/100km is quite excessive but its expected the ECU willl run the engine rich until a run-in period is exceeded. Over time as more KM go into the engine you should settle down a little but its not hard to send the ECU to a Japanese company for a re-maping if the consumption fails to drop.

Knightsports re-mapped the ECU in my old RX-8 & I actually scored 10lt/100km in highway mode as well as extra power.

REgards

Sorry I meant 30sec before you drive away not gun it...

 

[Mikey444]

I wait till the fast idle settles down before begining to drive. After that I just make sure I don't go above 3500 rpm till the engine is well warmed up.

 

[Austerror]

Other reasons for bad fuel economy could be:

Bad spark plugs (fouled or worn out)
Clogged fuel filter
Bad fuel (try running higher octane fuel)
Exhaust blockage
Incorrect tyre pressure
Engine not worn in yet
Heavy right foot.

The most common I see is flat tyres. They cause all sorts of problems. I warm up my Cosmo 20B for a good 5 minutes, longer in winter. Most of the time the car has not been driven for a week or more, so a good warm up time is essential. Then easy driving until normal operating temperature has been reached (no boost either until then).

So the warm up time does hurt fuel economy, however ALL cars should be warmed up before driving. the kids you see in their skylines that hit full RPM/Boost when cold ARE reducing their engines life time.

Anyway there is a list of things to check. Another useful test is take the car on a long freeway drive. 3 hours of 100km/h freeway driving will give you a useful economy figure. You could drive less, but taking the city part of the driving out of the equation will also remove any bad driving habits or negative influences from stop start traffic.

So that can also be fun. Drive to the beech or something. Record distance travelled and take note of how much fuel you can fit in the tank after the trip. If fuel economy is still bad, then maybe there is a problem. If economy is improved and near or at quoted economy then the car is ok.

Anyway lots of things to check.