zoom44

16mpg is quite normal when running around at 3-4k most of the time and never using 5th or 6th except on th ehighway. to get 17-18 you have to use 5th in town at 35 or so and 6th at 42-45 and above

mcsetech

These figures look impressive as tabulated. The actual driving MPG are quite different than your figures.

I've had my RX-8 for 6 months. IT ahs 19,000 miles on it now. The average MPG I get on the car is not even on your graph. At best on the highway I get 13 MPG and city 8 MPG. When it is a mix of city and highway it is around 10 12 MPG.

I bought the car thinking it would be a full time car, but honestly have parked it and only use it on the weekends, due to the MPG and several other problems with the car.

I can see you spent alot of time on this and it is very well organized. But as in anything figures are only figures.

Actual experience is a total different story.

Raptor75

Wow, someone who gets worst then me. I'm getting 12mpg city in the summer, 11.5mpg winter. I wounder if all the reflashs have made the mileage worst then the original car's programing?

Astral

I began keeping track of my mpg (each tank) at http://www.fueleconomy.gov/ (click on "Calculate and Share your MPG"). It then shows up when people search for 2005 RX-8 6MT, and then they can see "actual user mileage" in addition to the EPA estimates. I figured this is like a public service of sorts to potential buyers (plus kinda interesting for me to keep tracking of the mileage).

zoom44

first these are real world experiences posted by forum members.

second- no one that ever drove their 8 actually on a highway for a full tank on cruise at legal speeds in a gear higher than 3rd EVER got 13mpg on that trip. it is IMPOSSIBLE, CANT BE DONE. fill your tank get on the highway at 65 mph in 6th gear with the cruise set. get off at teh nearest fuel station after the ligth come on. there is no way on this green earth you ever get 13mpg like that. people get 9 mpg during AUTOCROSS weekends. 8 in town is BULLSHIT unless you go everywhere in 2nd gear with your foot in the floor board.

If thats how you drive all the time DO NOT come on here and blame your car- its the loose nut behind the wheel that is the problem.

Paul_in_DC

I'm suspicious that a lot of low mpg reports come from people who recently registered and have only a few posts. Hmm...

DrDiaboloco

...only that the most recent suspiciously-low MPG report comes from someone who registered last year and has around 375 posts.

Not that I believe the numbers, mind you. I call BS on any report that claims teens on the highway and 10-11 in mixed driving. My worst tank was all-city, with lots of stop-and-go and frequent hard acceleration and it STILL exceeded 13mpg.

13mpg on the HIGHWAY? I think not. I nearly DOUBLED that on one of my tanks.

zoom44

i really mean the car cant do it. youd have to be at 100% or more duty cycle on the injectors or have ahole in your tank both of which would generate multiple CELS

Paul_in_DC

I was thinking of the one with 8 posts actually.

I've achieved 10 mpg a couple times... but that was at the track. City I typically get 17, and 23 is the most I've gotten on the highway.

DrDiaboloco

I have no problem believing ultra-low mileage at the track... But 10mpg in MIXED city/highway? I call shenannigans.

Funny how 23 is the MOST you've gotten on the highway, as I've not had a single all-highway tank BELOW that number (granted this comes from a sample group of about 5 or 6 tanks). Maybe you just drive faster than I do.

Astral

I never had a highway tank above 21mpg. Most of my 80-100% highway driving nets about 20mpg, and this is mostly cruising at 70-75. I don't know how you drive on the highway, but I have a hard time believing people getting 23+ (e.g. 24mpg) on the highway. Maybe if I drove with windows up, A/C off and cruising 65mph, I would maybe then get 22mpg.

Paul_in_DC

Yeah - hopefully people don't drive thru town the way I drive at the track.

The 23 is the only time I've actually measured all-highway driving. I averaged 75 on that trip, and much of the terrain is hilly. That affects the mpg since it accelerates in the up-hill stretches. I would guess in Indiana the terrain is much flatter, so you should expect better mpg in that case.

Raptor75

I think a lot of the problems here can be attributed to the fact that one RX-8 can deliver very different mileage than another under similar driving environments. At the same time people are people and will make mistakes or misreport facts which further clouds the issue. The fact that Mazda seems to be dismissing this issue rather then dealing with it leaves us to further speculate. Here is my mileage reading since the car was new. I attribute a slight increase in mileage to summer vs Winter driving, I'll have to wait till next winter to confirm this. See attachment.

zoom44

not like there isnt witnesses to the 24 mpg tanks. i proved to nemesis 8 (lives up your way) tha tit could be done on th eway to sevenstock driving with cruise set at like 78. he was nervous but blown away when we got into the 340 mile range. the first tanks where i proved it to him i actually got 23.99 and he got 24.2 or somesuch.

Raptor75

I would believe this. I drove a 100 mile trip and based on some very rough estimates believe I was getting 20 to 22mpg on the highway. I was driving at a pretty steady speed. This car seems to suck down the gas far more then a piston engine in response to acceleration. Use the cruse control and you can probably hit the 24mpg. When I was enjoying the highway my mileage dropped to 18.

MPG > HP

The MPG killer on our '8s is that 4:88 rear end. My FCs would routinely get their best MPG (23-24) cruising at a steady 85MPH, because of their much taller gears (4:10?), even though they were almost 100HP down on the 8. I get 21+MPG on 95% freeways where my speeds range from 50 to 85, usually able to maintain at least 80 on the cc for 1/2 that time. Not what I expected 3 years and 80K miles ago, but then again, I really don't mind the added N/A HP to play with!! (All miles w/ AC - what little there is - on full time.)

DrDiaboloco, Have had 4 REs & MPG always got better, tho not by a whole lot (+.5-1MPG?).

DrDiaboloco

Yes, that would be true... Only my two highest highway-only tanks were from eastern Ohio to western NJ, one in each direction, on I-80. If you're not familiar, that is some pretty hilly terrain as Interstates go, esp. the western NJ to mid-PA stretch. Naturally I didn't do the exact same distance in each direction and stop at the same points, but both trips covered more or less the same ground, just a week apart (early May, very little AC use).

Frankly I was surprised the mileage was as high as it was, but it wasn't a one-off fluke. My mileage was slightly worse on flat land (IN and western OH), but it was also raining each time and I've noticed a precipitous drop in mileage on rainy pavement (even keeping speed more or less the same) with this and other cars I've owned.

DrDiaboloco

Any thoughts as to how vehicle mileage (and therefore the "age" of the engine) would affect mileage?

I've read that the rotaries kind of get more and more powerful as the miles pile up (at least that's what they say about the racing engines)... Would one expect mileage to improve or decrease with age?

For the record, my car still doesn't have even 4k miles on it yet, which is why I ask. My two high tanks were both achieved around the 3k point. I don't have my mileage spreadsheet in front of me, but in concept it's very similar to Raptor's, with date, mileage, octane, and driving style/road conditions. If anyone is even remotely curious I'll post it when I get home (several days from now)... Which will help jog my memory and correct possible errors in what I've posted so far as to best/worst mileage, average, etc.

Raptor75

I have heard that the rotary get better with age in regards to both power and mileage, long term reports in magazines seem to confirm this.

Please post you mileage info. I'd be interested to see it. Thanks

DrDiaboloco

Will do. I'm overseas right now but I'll post the info early next week... Once I figure out how to attach a thumbnail like you did. :D

Winfree

I calculate not by Miles per gallon, but distance before filling tank in comparison to the Mazda 323. The 323 holds about 12 gallons, if full at San Miguel, requires refilling at Frisco. RX-8 holds about 18 gallons, if full at San Miguel, requires refilling at Frisco - but we get there a lot faster - so for half a tank more than the 323, get speeds of 85+, and spend about $10 -15 more for a long trip in air conditioned comfort... yup this one is good! Much better on hills and also in wind, especially evil cross winds near Salinus - One really good note - Frisco gas prices were about 50 cents per gallon less than our local rip-off prices. Cheapest good gas in area - Morro Bay

gonnahanvan8

Umm, my Rx-8 doesn't hold 18 gallons. How is it that yours has an 18 gal tank?

DrDiaboloco

So you'd rather that we stop using accepted mathematical methods of comparing mileage and instead use nebulous "I can make it from point A to point B" tales that mean nothing to anyone who doesn't drive on your route? What relevance does "distance you can travel on one tank relative to a 323" have?

I think the rest of us will stick with "miles per gallon".

SecrtSqurl

I also thought the idiot light came on when there was 3 gallons left in the tank. When the light comes on, I always put in roughly 13 gallons.

DrDiaboloco

Ha ha ha... Somehow that part escaped my notice!

I don't have my manual in front of me, but I seem to recall the number is 15.8gal capacity.