10 MPG what the hell!?!?! please read post before killing it
 

Im not here to piss and whine about crappy gas mileage and how I can make it better because im not a ignorant cheapskate wanting a sports car with prius MPG. I just have a feeling I should be getting maybe 12-16 city. I run it between easy casual driver to hard core driving. maybe 70/30. With having purchased this car only a month and a half ago I, thinking it might not be a bad idea to have a compression check to make sure the engine is healthy. (or maybe im just paranoid)

Info on the car

2010 grand touring
19,600 miles (purchased with 17,700)
run it between 88 90 octane (checked mpg between both, consistent numbers)
ran through about 3/4 of a quart of oil after about 2200 miles (I check it daily, after running it hard, and every other fill-up) I use mazda 5w-20 per manf specs
I rev it up between 4-7000 rpm before shutting him off
I always allow him to warm up so the needle is at the second mark and i keep the rpms under 4000 until he is fully warmed up


I maybe a newbie, young, and it being my first car but Im doing what needs to be done and I just dont want this to be a early warning sign that i will ignore until the motor goes up in smoke and theirs not a mazda dealer in sight to replace the engine.

what do you recommend I can do to further look into this and diagnose.

check coils, leads and spark plugs

ive never had a problem but from reading the forum i have learbt that this is prob the cause for bad mpg, maybe you should learn to search and read before asking to be spoon fed the answers

Rage gave you the places to start....in addition..

You dont need to rev the car before you shut it off...especially up to 7k. Just shut it down like a normal car. IF that process was beneficial to 04-08s..you have a '10..u dont need to rev it.

You dont need to let the engine up warm up so long. Start it, wait 10 seconds and go. It is better for the car to warm up while moving, than just sitting still.

Good luck with the mpg thing.

as per usual... how (exactly) do you figure out you're only getting 10mpg?

and ...what are you talking about here...you use regular?

"run it between 88 90 octane (checked mpg between both, consistent numbers)"

Aside from what has already been mentioned, I have highlighted a few things that you are going to want to search on if you want your motor to last.

I've gotten 8 mpg before. Depending on how you drive depends on mpg. Straight hwy driving you should get between 240-300 miles per tank. 300 mpg going about 60-65.

I'm guessing that you just drove the car to hard. At what rpm to you generally shift at? I shift my 2010 R3 around 3000-3500 90% of the time and I consistently get 20 mpg. Also, you should switch to a higher octane gas, I usually get 93 octane, but if the station doesn't have it I settle for 91 octane.

as said before, check plugs, wires, and coils. You're likely due for 2 out of the 3, and replacing wires wouldn't be a bad idea either.

Other than that, do your research. Read the stickies on the site before you assume that what you're doing is right.


Moby, I doubt he's driving it too hard. I get about 16 combined, and the only time i shift at 3-4k is when the engine is cold or i'm still shifting to second down my long ass driveway. :lol:

I got about 7mpg on the track last time. He'd have to be driving pretty irresponsibly to get full on road course mileage. :lol:

Automatic trans and S2 models get better mileage than the S1 6spd.

Sounds like you are driving way hard. I get <8mpg on the track and you aren’t far off that. That or as the others have noted your may have some ignition system issues or maybe a leaking/faulty injector. Finally, your air filter is not likely completely responsible but if its in need of being replaced it will contribute.

Also, as has been said there is no need to rev that high on shut down if at all and there is no need to let idle to warm up. That just waists fuel and dilutes your oil. Need to warm up under light load.

Don't do this.
You are wasting gas for no reason.

Don't do this.
You are wasting gas for no reason.

Unfortunately, you're doing things wrong.
Don't do those two things anymore, and your gas mileage will go up.

When you start your car, let it idle for 30 seconds, and then drive gently until the first light goes off, and then slightly harder until the second light goes off.

New plugs and wires, just to rule those out.
If you have the money, a new set of ignition coils, and that will complete the trifecta of ignition components.

How long is your drive to work? Lots of stop and go, or all highway?

BC.

You have lights in s2 for temp?

Hes referring to the rev limiter lights in the tack with the first cut off being at 5K and the 2nd at 7K.

Oh that makes sense.

I just added my fuel ups to fuelly and at some points I was getting 12.9 mpg all highway last week. That was going 90. Usually going the speed limit and behind 18 wheelers I can get 23-26. My tire really need balanced which probably would make a difference.

You're wasting gas by warming up the engine. You're also wasting gas revving it before shutdown, though the warmup procedure wastes a lot more gas. Just get in and drive the car. The variable redline is there to keep you from damaging the engine; if Mazda really thought the engine were completely unusable at room temperature, they would've installed a block heater from the factory.

I do rev my engine before shutdown if I just move the car from one parking space to another, but that's it. If the engine has at least a couple minutes to run, there is no chance of sparkplug fouling.

GOOD grief..STOP this silly advice some of you...

The OP's car is a 2010 and only 19K in miles...

OP, you do not need NEW Coils or Wires, this is just bad advice.

You are not complaining of poor performance, or engine missing are you?, just MPG.

And Yes OP, you are being paranoid..

Now, STOP the BS of revving the car BEFORE turn off, STOP it NOW, Totally Unnecessary.:)

Engine Warm up, will not hurt your rotary and IMO is a good idea for a short time, until first LED Tacho Bar turns off (about 2-3 minutes).

IF 70% of your driving is PLUS 5500 RPM then yes you will get this sort of MPG, drive ANY performance car at 70%+ of engine power/capacity and see what MPG you get.
What also confirms this is the amount of Engine Oil your are using to lubricate Apex Seals...

Apart from a few things like Tire Pressures, Fuel octane and perhaps Spark Plugs (I would renew them, 20K at the RPM you are using, renew your spark plugs).

You said you are young, IMO you have a lead foot, and will get this sort of MPG.

+1 on that. 19k mikes should only need plugs and that is a maybe.

And switch to 91 octane, keep it under 4000rpm as much as possible, spark plugs would not be a bad idea but they are probably ok.

Reving a rotary is 3x more gas consuming (exponential as the rpm go up) than a piston engine because of the conception, and low torques means as soon as your accelerating, your maxing out the output so as bad as wide open throttle.

Fun fact: did you know at 9000 rpm it consumes 60L per hour? 1h at the redline and your gas tank is empty lol

edit: I could maybe add a engine air filter? start with that, can help alot if its clogged up

Another RX-8 myth. That procedure was NOT NECESSARY on '04-'08s in normal use. Only for when the car was started up cold and then turned right off (moving it from the garage to the driveway to be washed, for example).

40 years old, drive it like i stole it, happy to see 12-15 mpg avg.

There's lots of stuff to fret over in life, the MPG on the rx8 is right below "is that a grey hair growing out of my belly button?"

It's good that you're checking your MPG but unless you see a huge drop then don't worry about that unless other things are also going wrong (ie. CEL's, strange noise, vibrations, higher/lower then normal oil consumption)

You'll get use to the well meaning but often ill informed advice you will get from this forum and develop a knack for weeding through the BS.


Happy rotoring.

Classic M8...rofl...:)

Perfect...

Yeah. Hes approaching 20K and going in for a full circle maintenance work up at the dealer soon. Ill go ahead and get the spark plugs taken care of. And where do you find 93 octane. The highest I can usually find is 91 in my area but most fuel stations carry 90 as their highest. Is their an additive to increase the octane from 91 to 93. I generally warm it up until it the needle is on the second marker and the first red line limiter is off. And I drive it under 4k RPM until the last limiter is off. after about 2200 miles ive gone through about 3/4 of a quart of oil. I havent seen any check engine light. Only a check tire pressure and its probably from a faulty sensor since I checked all tire pressures and converted my tires to nitrogen filled.And its going in to get that looked at. And as far as shifting. When im in automatic I just let it shift between 3-5k, when im being a speed demon and in manual mode I shift at 6500 to redline.

And my concern with the gas mileage was if it could be a sign of something bigger. I have done alot of research before buying this car and I am absolutely head over heels with it and I dont want him to have a short life. I dont care if the gas mileage is horrible because I knew going in. I bought it because it is a car that makes me smile even when I walk up to it.


So for the 2010 you dont have to rev it before shutting down?

You don't have to do that for any RX-8.
It's advised for '04-'08s, at least, for the rare situation of starting a cold engine and turning it off a minute or two later (e.g. you get up in the morning, go to the garage, start your 8, pull it out of the garage into the driveway to wash the car, and turn the engine right off. Then you rev it before shutting down.

I always just drive around the block once or twice until the light shuts off, in those cases.

BC.