Does anyone who now has their 8 have any stats on fuel consumption? Please state if you've got the low or the high power and whether it's an auto or manual.

Also, can someone tell me if the car comes with a trip computer i.e. mpg, external thermometer, number of miles that can be covered on the remaining amount fuel....

All advice greatly appreciated.

 

Try here. & welcome to the forum.

 

Thanks Lensman, but that thread it's mostly full of guesstimates. I was after someone who actually has a car and been through a few tanks.

The dealers are quoting about 25mpg.

 

i don't mean to seem stupid, but why is the engine so seemingly inefficient? in all the literature i've read on the RX-8, Mazda and others mention how much more efficient the "Renesis" is over previous versions, and they mention how the design of the engine (no conversion of linear energy into radial energy) is better, and how the engine is lighter, fewer moving parts, etc. Everything they say makes the "truth" (19-25 mpg) seem very startling. I mean, just about any MUCH heavier V6 car with an engine with more HP gets the same or better gas mileage. Am I missing something? I love the rotary concept, and everything about it and this car makes me feel like it should be a lot more efficient than everything says it is. Just wondering if someone could share why it isn't?

Q

 

My first tank of gas got me 16.1 miles to the gallon. That was with a lot of idleing and ogleing everywhere I parked and 90% in town driving. So I feel relatively sure this will be my worst case scenario. Winning Blue, 6MT, GT package, constant air.
Other Questions: No on board computer to track consumption. It does have an external temp gauge and internal display.

 

Thanks RX8-U-UP. Shame about the on-board computer :-(

But still, does anyone have a few tanks worth of info??

 

Ouch, my FD gets that in the city if I stay off the boost.

 

I'm not any kind of rotary expert, so maybe other people will correct me on this, but my understanding is:

1) Rotary engines are inherently less thermally efficient than piston engines of the same capacity due to the very flat shape of the combustion chamber. This gives a high ratio of surface area to volume and this allows more of the combustion energy to be conducted away as heat, rather than converted into useful work.

2) Earlier rotary engines also wasted fuel by sweeping some unburnt fuel out of the exhaust port. The side ports on the Renesis no longer allow this to happen, so Mazda is correct in saying that it has improved the fuel consumption. But it's still not great.

3) Rotaries ARE very efficient in terms of the amount of power produced for a given physical size (not displacement) and weight of engine. This makes them good engines for sports cars where you want lots of power without too much weight (to preserve handling balance) and fuel consumption is less of an issue. And then there's the smoothness, high revving nature and linear power delivery which are fun in themselves.

 

Rotaries eat up gas at idle.

 

Why not insulate the engine to reduce heat loss?

 

Because then the motor will blow up from overheating due to trapped heat. Once the gasoline is converted to heat energy, there is no way for the engine to convert it back to a usable energy source. The idea is to reduce the amount of heat produced, not trap the heat.

 

So I guess from a size and weight standpoint, one can say the Renesis is efficient. Creates plenty of power for its size. But from a fuel consumption perspective, it is not efficient. It creates lots of wasted energy in the form of heat resulting in lower MPG. It makes a form factor like the RX-8 possible but we pay at the gas pump. Perhaps future generations of the Renesis will improve on this.

 

I think it would be interesting to compare vehicles based on miles per gallon per horsepower. Or even miles per gallon per horsepower per liter. :D

 

That would be my take on it. However, I think people do sometimes exagerate the fuel consumption issue. I read a one page review of an RX-8 in a British magazine a few weeks ago and they mentioned poor fuel consumption three times. A couple of weeks later they reviewed the 350Z at much greater length and never mentioned fuel consumption at all. And yet, according to official UK figures, the two cars have almost identical MPG.

Rotaries have a reputation for poor MPG, but some V6's are as bad (every Alfa Romeo V6, even the 2.5, is similar to the RX-8). Unfortunately, poor MPG is one of the few things that everyone "knows" about rotaries so it does rather get done to death in every review.

 

but it's true, wankel engines have poor consumption efficiency... when you're talking about a race engine, that's different (where the R26B had pretty darned okayish consumption, in context), and when you're talking about a sports car, who cares??

a wankel will never be as good as a piston engine on consumption efficiency because of the nature of the mechanics (extremely oversquare, as was mentioned before lots of surface area to volume in the combustion chamber, etc etc) inherent in the design... BUT that doesn't mean you can't drive your car to get better consumption rates than someone else: if you drive to consume as little fuel as possible you won't be doing poorly by any stretch, but if you drive it to have fun you'll be eating a lot of fuel, no matter what car you have. the RX-8 might be a little higher on both accounts when compared to something with a VQ in it, but there are many many other factors which can impact fuel efficiency.

 

Just filled up for the first time, 6MT 18.9 MPG with 70% city
driving and 30% highway, 270 miles on a tankfull. Engine feels
as though it is beginning to free up. Hope the mileage improves
with the next tank. Love the dead pedal footrest. It is very
comfortable while driving and did not expect this. My first car with this feature.
2nd tank 19.0 mpg
3rd tank 18.2
4th tank 17.6 higher rev's

 

Concur about that footrest. What a delight! After 6 years driving an Odyssey minivan with nowhere to put my foot this is so welcome. One of those unsung touches that really makes driving the 8 pleasant.

 

im dissapointed in the fuel mileage (rx8 book claims city 20.4 and hgy 30.2 epa estimate) they werent even close with 18 and 22 on the window sticker.this is almost the same as svt cobra 390hp sc v8.the cobra has a 1000.00 gas guzzler tax.im still going to get my rx8 but i just dont see the so called 40% improvment with these numbers.i hope we can get better than this.

 

Has to be more than 22 mpg on the interstate. I managed 26 in the FD from Dallas to Baton Rouge, and that was with several bursts up to 150 or so.

 

my mileage is pretty shitty so far. i have 120 miles and the mileage is already down to 1/4

 

Well, I just got mine and it's already at close to half tank with only 100 miles! Either I have a heavy foot or the gas just seem disappear for no reason. But I'm not complaining :p But I think the 6th gear crusing on the highway would help less gas consumption.

 

It depends a LOT on how you drive it too!

I just sold my Nissan Spec V. 2.5l, 4 cylinder. The way I normally drive I got around 18mpg to 22mpg around town. It is a SPORTS CAR, dammit!

OTOH, I did try babying it a couple of times and got around 25mpg.
So, maybe you can get better mileage if you baby a piston engine, but it is a moot point for me..

 

really dont understand why everyone is so hung up about the fule issue. Manufacturers, and even Gov figures are well known as being mere statistics that seldomn have real world applications. Sure, they can be relative as a means to compare, but YOU will make far more impact, and your driving style will do more to determine the actual figures than any test.

They are largely irrelevent, and in a sports car even more so. As long as YOUR car is close to others in its performance bracket, thats close enough!. Here in the UK the AA found a Volvos fuel consumption to be 44% BELOW that claimed in Gov and Manufacturer tests.

ENJOY the 8`s rotary for what it is, not for what it isnt. If fuel consumption is a BIG issue, buy a diesal!.

 

I don't think it should be a crime to want to have a nice car even if you do a fair bit of mileage. I do nearly 20,000 miles so every mpg counts. I drive a BMW 3 series Coupe and get on average 35mpg (UK gallons). By varying my driving style and can watch it move between 28mpg and about 40mpg, but at least the BM has an on board computer so you know what you're doing.

I want to get an idea what the 8 is capable of - obviously everyone is going to have fun with the car but I want to know what that's going to cost me, and also what's possible if you behave yourself on the motorway.

 

Oh, by the way - I'm from the UK where standard fuel (not the fancy stuff) costs about $1.30 per litre.

At 20mpg and 20,000miles per year that works out at about ....

$6,400 of fuel per year!!!!!

That's why I ask the question about fuel consumption...