i'm at 750 miles or so, last tank was 16.1 mpg 91 octane from union76, getting better than the 13-14mpg i started off at =)

 

I'm not saying to redline it, but rather the best way to warm any modern engine is to drive the car. Idling is horrid for a vehicle - there is little airflow to cool the engine and none to cool the exhaust system. Letting your car idle for five minutes every morning is a good way to be on the road to a new catalytic converter early.

 

I picked up my 8 in Nova Scotia and live in Newfoundland - 1350km (~845 miles) from home. Immediately left the dealership and put all highway miles on it.

Fuel consumption results:
160 litres of 93 octane consumed (42.27 US gal)
1350 km travelled (all highway) (844 mi)

19.96 mpg highway - not nearly as good as I would have hoped. Any thoughts?

 

Just what others have mentioned - conventional piston-engined cars tend to see their MPG improve over the first 3000 miles or so. I suspect the rotary's mileage will also improve as the apex seals break in.

 

Oh, well 5 minutes is excessive, but a modern car is not ready to go when you have out on your seatbelt. I know my FD makes some funny noises until it gets to about 100°f, which takes at least 1-2 minutes.

 

For those still keeping track, just got 17.3 mpg over about a tank and a half. This makes my mpg since buying the car: 17, 15.3, 16, 17.3. At least I'm on an upward trend after an initial dip and still not driving like a grandma. I run A/C at least half the time, punch it when I want (which is pretty often), cruise at about 80 mph, and my last tankful included the Great San Diego RX-8 Rally which was a lot of twisties.

(whoa, I just figured over the last tank vice 1.5 tanks I got 18.2, so I really am feeling better now. If I start averaging 20 I can shake that SUV-morality guilt complex.) Also, for the sake of full disclosure the last 1.5 tanks was 91 octane; I just filled it with 87. We'll see.

 

16.5 mpg on first tank. The low fuel light seems to come on with more than
2 gallons to go.
50% city vs. highway.

 

I wouldn't call your FD a modern car, either...

Most any new vehicle's owner's manual says warm up is not necessary, just drive gently until the car comes up to full temperature...

 

I got around 17.10 gallons on my second tank. It was mostly city driving, to and from work and so on.

I'm going to keep track of this 3rd tank, and see how it goes as well.

 

Just one other thing - the disclaimer from the bottom of the EPA mileage estimates of 18 city, 24 highway states:

 

I mentioned this in one of the dyno threads. When one member ran his car on the dyno and recorded his Air/Fuel ratio, we noticed that the car went rich in the upper half of the rev range. There is speculation that the less than advertised HP output is due to the ECU being tuned differently for the first several thousand miles or so while the engine breaks in (which would explain why dealerships are telling people to drive the car normally, just avoid hanging rpms for awhile).

I wonder if this possible protective over-rich situation is also why the fuel economy is so poor on these new engines, and it will improve once the ECU changes over to normal mode...

---jps

 

Conversely, if you need MPG, just take (234.7) / L per 100km.

 

Sputnik, good connection... a temporary rich-fuel-map-for-break-in ECU mode would indeed tend to waste gas. To me, both the low-dyno and low-fuel-economy (relative to Mazda specs) observations/concerns that new owners are having are very interesting -- I can't wait for the truth to come out, which may be difficult to get to. If the 8s operating software truly evolves with mileage, then that seems hard to test. Hopefully Mazda will eventually explain one way or the other (i.e. YES, program behavior is catered to mileage -- or NO, all algorithms are fixed).

I bet the first company that engineers a "chip" for the 8 will realize the truth during R&D. Furthermore, it will be interesting to see what a chip will do for this naturally aspirated coffee grinder, err... RENESIS. IMO, if a chip gives it more than 10 hp, then we know that Mazda has these conservatively tuned. After all, with a "different" design, there is extra emphasis on proving reliability. Problems with a convential engine in a new car could be attributed to a production line hiccup, but with the 8s alot of people will scream "f---ing Wankel!" and then a "those things don't work" reputation will be off and runnning...

Woah, long post... sorry to waste all those bytes.

 

I have to admit, this is all new territory to me. Notdeaf, are you saying that aftermarket manufacturers could make a replacement chip for the ECU? Is this something that commonly happens on different makes/models? If so, is it hard to install, does it void any warranties, and can you get different chips tuned to performance and/or economy? This is probably yesterday's news to y'all but to me it's a new concept. Thanks!

 

Tank #5 - 93 Octane:
311.4 Miles * 13.416 Gal = 23.21 mpg (best yet for me)

My type of "typical" driving: 70% highway w/ no revs above 6K

Trying my 1st tank of 91 octane now.

 

1st Tank averaged out to be 14mpg (total 229 miles)
2nd Tank averaged out to be 17mpg (don't recall the mileage)
Working on the 3rd tank ...

But keep in mind the car started with 4.5 miles on it and over time it seems to be getting better (not to mention the 1st tank dealt with some harder driving than the second too - hehehe)...

Most of my driving has been highway; however highway in Charlotte doesn't say a lot. Typical morning and afternoon commutes tend to include a lot of stop-and-go traffic conditions because of backed up interstates...

We're going to be taking a trip from Charlotte NC to Williamsburg VA in mid-September and we'll be driving the RX8. It'll be interesting to see how well she really does out on the open highway versus driving around town and daily work commutes.

Keep the data coming in so we can all see how we measure up !!!!! :D

 

I've read through about 50% of this thread. I'm not really seeing the increased mileage of the RX8. My FD gets 12mpg in town, I know that is much worse than the RX8 but I drive the hell out of it. If I stay off boost I get 15mpg in town.

On the freeway I just completed a 291 mile trip from Seattle to Eugene, mileage was 23.1mpg. Typical highway mileage is 21-23mpg.

Seems like the 8 is barely hitting that?

 

Most likely.

Quote:

Is this something that commonly happens on different makes/models?

Yes, with varying results.

Quote:

If so, is it hard to install...

Normally, no.

Quote:

...does it void any warranties...

You betcha!

Quote:

and can you get different chips tuned to performance and/or economy?

Normally, the car is already tuned for the best economy and reliability from the factory. The tuning on an NA engine normally advances timing, changes fuel maps, allows for higher rpms, etc., all in the name of performance. Normally, for a simple chip replacement, you aren't going to be able to dictate what you want.

---jps

 

OK, for my second tank of gasoline, I got 18.39 MPG (didn't record the first tank).

Mostly city driving, with AC on most of the time. Pretty aggressive driving (I had to respond to a VW Jetta who did a Jack rabbit start on a freeway on-ramp. I had to respond to put him in his place and uphold the RX-8 honor) so I red-lined "unintentionally" before my 600 mile break in period. Oh well, it was worth it! :D

My next tank will probably be better, as I'll probably drive a little more sanely!

 

Second tank for me was is 18.1 mpg

 

Filled her up yesterday and did a check ... 7.071 gallons at 125 miles on the trip meter averages to 17.667 mpg ... Again, that's driving with a lot of idle and stop-and-go traffic. :D

 

Does your city driving involve a lot of stop-and-go along with idle driving?

Charlotte NC is well known for it's horrible interstate commute weekday traffic ... Imagine a 3-4 lane interstate being a parking lot from 7:15am until 9am and 4:30pm until 6:30pm ... It's terrible ..

I wouldn't even say that my daily driving really classifies as city driving to me because the car's RPMs are constantly up and down for the majority of time just due to stop and go at short distances... A lot of times shorter than a typical block.

 

That sounds pretty good. At least you've broken the lower spec. I'm still trying to get there :-) ... 17.667 is the highest for me thus far...

Are you driving an AT or MT?

 

Well here are my first three tanks:

93 octane everytime.

19, 18.5, 18.3. I am going down for some reason. We are in Atlanta with stop and go commute and high A/C use, but still there is a fair share of highway everyday and nontraffic night driving(with no A/C). I can't get that 23 etc that others are getting.

 

Filled up for the second and third times yesterday, before and after a decent thrash on the countryside.

Second tank: 11.22 gallons for 200 miles of city driving - 17.8 mpg
Third tank: 10.47 gallons for 188.4 miles of high-speed highway and enthusiastic twisties - 17.99 mpg.