Razz1

I fell sorry for those who bought this for city driving.

Plain and simple this is not a city car.

Raptor75

I guess I missed that in the advertising.

CarAndDriver

I went 70MPH highway for about 76 miles and only got 21.3MPG. Yep, post recall has lowered my highway MPH.

DrDiaboloco

How did you determine this? Top off your car, drive for 76miles, and then top off again with 3-ish gallons?

PhotoMunkey

As a follow-up post to my own post, I have to note that the high desert temps have fallen off to winter-time 60's, 70's, and 80's out there AND, contrary to what I expected, gas mileage across the desert did not improve. This I fear rules out external temps as a primary cause.

Pre-mix DID appear to net 1/2 a mile per gallon better average during both the "poor" portion and the "good" portions of my trips. I've now had the emissions recall performed and the car is FANTASTIC in the mid-range RPM! Before, I could do 70 mph and get 17 miles per gallon, or I could do 90-95 and get 18.5. Across the same section of desert. I attribute that to the lack of proper cylinder oiling at lower rpm and light throttle. The OMP settings change at different higher rpm, and driving in that range yielded better fuel economy.

In talking to a few others on here it was mentioned that there's a "cat preservation mode" where the ECM sends the A/F ratio plumeting from 14:1 down to 10:1 when cruising above 4100 RPM for more than 15 seconds at a time (without moving the gas pedal). Since my desert cruise does just that (though at a slightly lower RPM), this is what I think is happening. On some cars, the ECM is seeing a condition it thinks needs "Cat Preservation Mode" and jumps to it, essentially removing the O2 sensor controls and running very rich. In LA traffic, hills, and turns, the ECM never sees the 15-second tripwire, and so runs happly lean the entire time. Just try to do a constant speed in LA traffic for any length of time! With the off-throttle coasting down hills in LA, the fuel economy picks up into the 20s, with the highest so far being nearly 22.

Taking this thought into account, on my last trip to LA I spent time off the cruise control lifting my foot off the gas slightly every so often. I averaged 19.5 on the way out. On the way back, with the new tune, and driving with the cruise set for a comfortable 82 mph, I averaged 19.2, with 5 blasts up to the range of 120 mph or so! Now I just need to cool my hot foot down and see what this tune will produce when lightly cruising the entire way across the desert. Hopefully, on the way to Sevenstock this coming weekend!
Eric

CarAndDriver

Yep. Filled up before I got on the freeway and when I got to my destination I filled up. The gas stations are on the way to/from where I traveling. It was a MPG test to see what I would get.

maxxdamigz

iTrader: (1)

posted for future reference by me:

I drove from NJ to OH and back in the 8.
I would say it was between 80-85 degrees on both drive days, sunny, and no traffic. This was in late July.

Mileage on Tripmeter/gal/$$/mpg
000/12.543/40.50/19.294*
178/.874/28.92/20.059
366/8.962/29.09/20.978
611/13.10/41.92/18.702**
642/2.709/8.40/11.443***
890/11.819/38.52/20.98
1183.7/13.0/42.00/22.592****
*reset meter at 242 to begin trip
**got to location so includes some local driving
***a very spirited cruise through some farm country in the middle of nowhere
****personal record

With the exception of the cruise, I did most of this with the A/C on low and windows up. On the rare occasions when I find a suitable place to have some fun, I usually drive with the windows down to better hear whats going on.

The 11.4 is also a personal record of sorts. I might be able to get into single digits at an autocross.

DrDiaboloco

The reason I asked was that such a small amount of fuel added to fill the tank can introduce a HUGE error in the mpg calculation. Not that your observed mileage is remarkable either way (though a bit on the low side from MY experience), but the level you "fill" to changes from tank to tank and a 3gal top-off isn't a good way to measure your mileage. With a 3gal fill, the difference of only a pint either way can change your calculated mileage by 1mpg.

Then again, for all I know, you filled it until fuel was running down the side of the car on both occasions, just to be sure.

DrDiaboloco

...and I think this is an example of what I'm talking about. It appears this record low mpg for maxx is calculated from a fillup that was only 2.7gals.

Again, I'm not debating that these low-volume top-offs ABSOLUTELY are off by huge amounts, but the possibility certainly exists.

Chasvo

As much as I love my 8, poor gas mileage is putting a damper on my enjoyment. Having owned an 85 RX7 for 10 yrs, I absent-mindedly bought the 8 after ditching a 2001 Jeep Cherokee this summer due to poor gas mileage as a commuter downtown to work. I did compare posted gas mileage for my old RX7, Jeep and 04 MPV as folows:

AUTOMOBILE PUBLISHED MPG
CITY / HWY/ COMBINED
MAZDA CANADA -RX8 - 18.4/ 25.6/-
US DEPT. ENERGY-RX8 - 18/ 24.0/ 20
MAZDA CANADA-MPV - 18/ 25.0/ 20
US DEPT. ENER-JEEP 2WD - 16/ 21.0/ 18
US DEPT. ENERGY-RX7 - 17/ 24.0/ 20

Well, the fact that it was better than the Jeep was all it took and since it was potentially better than all the others too was a bonus......well, I've only mannaged to record 7 fill ups since acquiring it in August but considering I drive 60 km a day with at least 80% hwy, it isn't as good as the numbers posted above. After the flash it seems to have dropped another 10-15% which really sucks.

L/100km/ Diff. City/ Diff. HWY/ MPG/ MPG(US)
12.8/ 0%/ 39%/ 22.0/ 18.3
13.2/ 3%/ 44%/ 21.3/ 17.8
13.7/ 7%/ 49%/ 20.6/ 17.2
13.6/ 7%/ 48%/ 20.7/ 17.2
15.4/ 20%/ 68%/ 18.3/ 15.3
14.2/ 11%/ 55%/ 19.8/ 16.5
16.1/ 25%/ 75%/ 17.6/ 14.6


What you see above shows a drop in the last 4 fill up after the flash(in bold). When compared to Mazda's posted mileage for city and hwy, it used to vary between 0-7% and 39-49% respectively. Now it's as much as 25% compared to city and 75% compared to hwy. I figure with 80% hwy I'm somewhere around 40-50% off the mark. Personally I think this is way to far from published..it's criminal!

CarAndDriver

Well I have a longer highway trip coming up, so I'll see later this week.

I do notice that the RX8 fuel tank design easily tops off quick and spills down the side of the car. You learn to basically end fueling at the first click off of the pump handle.

CarAndDriver

I think my mileage has dropped post recall work as I've stated before. It is amazing that some people have had MPG increases. Wish I was one of those folks.

I've seen a drop of 2 MPG on the highway, which is about 10%.

DrDiaboloco

My experience with this car over the last 8mos has shown that it also depends upon WHERE you top off. Sometimes it will take very little after the pump clicks off, and in some places it'll take an extra 3/4 gallon. I wish I'd paid closer attention to when/where/how this happens... I've taken fuel in at least a dozen states and I wonder if there's any consistency on that basis, mostly in the states that have those accordion -shaped "collars" on the pumps. Never mind the reality that you can't even be "in charge" of your top-off in NJ because they won't let you pump it yourself (I know NJ isn't the only state like that but I can't think of the others).

CarAndDriver

I'm just constantly wary now of getting petrol down the side of the car.

Oregon is another state I believe.

Paul_in_DC

It all depends on the sensitivity of the pump. Some are more sensitive, some less.

One funny experience... At one place with "those accordion-shaped collars on the pumps," when it was full and clicked off, it jiggled the handle enough that it suddenly popped out of the hole and onto the ground. It kinda looked like the 8 said "Okay, I'm full... paTOOEY!"

Astral

I never tried to top off the 8. I always stop when the pump stops, thinking that they stop about the same range... but it's true, some pumps stop really close to full and some have that extra half-gal to go. This is probably skewing my readings a little.

(Although, if you go to the same exact pump and stop at the first click--then that should be consistent.)

I was tempted to top it off, but I don't want to spill gas down the side of my car.

I've done that once in my Mazda Protege .. not fun.


If you want to go for the extreme top-off, if you run the pump at very low speed (barely depressing a handle), the auto-shut-off occurs a lot later, and I was able to squeeze out the absolute max that way back in the day, to the point where I overflowed my Protege's tank.

PhotoMunkey

Most all of my mileage estimates have been over runs of 130 miles or more. I'm fortunate enough to do most of my work from home, so "commuting" to me means zipping out to LA to photograph some cars, then zipping back home.

It looks like I'll be hooking up with the "Desert Caravan" to Sevenstock when they pass through my town on Friday. I'll be extremely interested in everyone's mileage crossing the rest of the desert into Palm Springs. This would be a good time to see if 33 RX-8s, all cruising at the same speed during the same atmospheric conditions on the same road can reproduce the fuel economy I'm seeing aross this stretch of desolate countryside.

DrDiaboloco

Heh heh... Sounds like a scene from the movie "Cars".

Billy Massacre

Great work Norton! I thought that i just had a leak in my fuel tank but it would appear that i am not alone!!

I have heard that cruising at about 4000 rpm is optimum for fuel economy when cruising around - Does anyone know if there is any truth to this?

msrecant

I have just gotten the recall flash so I updated my spreadsheet and came up with the following MPG numbers until this point:

July 2003 Port Flash - 6,567 miles 14.9 MPG

M Flash - 8,375 miles 16.4 MPG

R Flash - 6,955 miles 16.5 MPG

I do mostly in-town driving and I drive in a spirited fashion. My car is totally stock.

jburns

Chart format gets lost when posting but here is the total history of my 06 fuel use. Pretty consistent with an average just over 19mpg. I have a heavy foot and use it.

Purchase,Date Price,($/G),Gallons Purchased,TotalCost, Odometer(miles) Station, FilledTank?, MPG
8/7/2007 2.889 13.155 $38.00 4,924 Kangaroo Y -
7/31/2007 2.999 13.341 $40.01 4,683 Citgo Y 18.32
7/23/2007 3.079 13.805 $42.51 4,438 Citgo Y 18.36
7/22/2007 3.109 10.937 $34.00 4,134 Citgo Y 22.02
7/15/2007 3.039 13.737 $41.75 3,928 RaceTrac Y 18.84
7/8/2007 3.119 12.665 $39.50 3,646 Citgo Y 20.53
6/28/2007 3.169 13.096 $41.50 3,385 Citgo Y 20.61
6/9/2007 3.249 12.927 $42.00 3,141 Citgo Y 18.63
5/29/2007 3.279 13.570 $44.50 2,904 Citgo Y 18.33
5/20/2007 3.229 12.545 $40.51 2,662 RaceWay Y 17.83
5/15/2007 3.189 13.012 $41.50 2,401 Citgo Y 20.81
5/10/2007 3.069 13.362 $41.01 2,145 Kangaroo Y 19.67
4/27/2007 3.139 13.857 $43.50 1,897 Citgo Y 18.56
4/19/2007 3.099 12.584 $39.00 1,649 Citgo Y 17.90
4/14/2007 3.239 11.964 $38.75 1,393 Shell Y 20.34
4/9/2007 2.999 13.188 $39.55 1,161 Citgo Y 19.39
3/31/2007 2.699 13.763 $37.15 915 Hess Y 18.65
3/28/2007 2.729 12.825 $35.00 622 Kangaroo Y 21.29
3/26/2007 2.719 12.871 $35.00 379 Shell Y 18.95
3/22/2007 2.629 12.933 $34.00 144 Crown Y 18.26

Total Quantity Purchased (Gallons) Total Cost ($) Average Price ($/G) Average FuelEconomy (MPG) Total Fill-ups 260.137 $788.72 3.034 19.33 20

psonoda

My first measured fuel tank milage is ONLY 14.3. I realize that 95% was city and it was hard (Just picked up my used 2004) but this seems low. It have been hot mid 90's. Any thoughts?

jayman

I have an 04 I just picked up in July. If I do mostly city w/air I got 15mpg. If I don't use the air and do 50/50 city and highway I get 20. On highway only I get 23 or better.

chavy85

ok so i bought an 06 Shinka, and took it on a rather long road trip this last weekend. what i have seen is that the hotter the temp the worst the gas mileage. i went from Corona Ca to Durango Co. and from the AZ border to the NM and CO border i was getting average 24.5 mpg. with a few fill ups at the 27 mpg mark. i broke the 300 miles per tank a few times. but as soon as i was on my way home in the heat. it went to 19-21 mpg.
most of the highway driving was at 90+ in 6th gear. so that is what 4750 rpm. or there abouts. so the comment about running rich for over 4500 rpm over long runs i would say is wrong. although the temp makes sence to me. or it's the sh*ty gas i got in CA.
i now have just over 10K miles on mine. bought it with 7800. and used 1/4 quart of oil.
happy trails and keep er safe.

HR

MPG > HP

chavy85, Consider yourself lucky. After 88k miles, my 08/03 build only once got 24.5 on an unusual string of consecutive 65mph runs. Based on the conditions you describe, my mileage would be about 17-22 rather than your 19-27. Although I've applied all of the ECU patches and followed most MPG discussions (note my handle) from the beginning, I don't recall any significant design mods that Mazda has announced that would make up the difference in what you (and what seems to be most '06s and beyond) and my old build models make for MPG. MPG aside, you won't find a finer handling marque, especially at the limits!

Anyone, Have I missed something that would boost my MPG by a mile or two? Not that it matters much to me, other than due to design curiosity, as I now drive an '06 Prius and only take the '8 out for track days. Once you've driven a true hybrid, it just seems pointless for a daily driver to not recover energy during braking or go electric only, in jammed/slow traffic. Plus, you can't deny Toyota/Denso's win out of the box in their first 24 hour endurance run with a capacitor hybrid prototype. Makes the Audi LeMans diesels look like pikers. Read the writing on the wall.