Last post on Jun 03, 2011 at 11:23 AM
You are in the Mazda RX-8
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Mazda RX-8, Fuel Efficiency (MPG)
#73 of 96 Re: The new federal millage rating system [trispec]
Jun 04, 2007 (8:34 am)
I own both an 05 S2000 and an 05 RX-8 (6 speed).
I just came back from a trip to the mountains in the S, over 30mpg on the highway (all top down) and 26-29 mpg driving around the mountains (all top down). I get 24 mpg commuting to work (mostly all top down).
My RX-8 with the latest recalls and computer flash gets 14-15 mpg commuting (same route as the S gets 24 mpg) and gets 19 mpg on highway trips - though one time I got 20.5 mpg. And highway driving is mostly set the cruise on 74 or 75 and just ride - so not much room to improve the mileage except to drive slower.
So it does not matter if you use the old or new EPA numbers, when driven as intended the 8 suck fuel like a huge v-8 (or worse). So says all the car mag tests and so say the customers who drive (the 6 speed) in a spirited manner.
In a recent C&R head to head with the 2007 Ford Mustang Shelby GT, the 2007 Mazda RX-8, the 2007 Nissan 350Z, and the 2008 Audi TT 2.0T guess which car "won" the test? Even though it "guzzles gas like a private jet" ?
link to story
Note on their 600 mile test the 8 returned the worst mileage at 15mpg - even lower than the 319 hp Shelby.
I love the car, like C&D I think it is a "winner", but when driven as designed the MPG just sucks
#74 of 96 Re: The new federal millage rating system [dwynne]
Jun 04, 2007 (5:49 pm)
Well MPG isn't much of point to push with the RX-8, but my paddle shifter RX-8 AT seems to get better than your 6 speed RX-8 MT. For example, I average 80MPH on my Boston to Portland evening run and fill up to fill up I get 23MPG. I have gotten 25MPG on a steady 60MPG runs to the Cape. My work commute these days is running 18MPG.
I don't do much paddle shifting any more though, so that may help keep the RPM's down well below 2000 most of the time. I do regularly rev past 5000 and oil consumption in the city is a quart/1000miles.
Thanks for that link. I sure love my RX-8. It still turns heads, especially when four 6' adults exit with all the door open.
#75 of 96 rx8 v 350z mpg
Jun 11, 2007 (2:42 am)
Yeah I agree the RX8 is an amazing ride, just too bad the mpg and lack of torque (no faster than a Nissan Sentra Se-R). I drive a 350Z and normally get 28 mpg at hiway speeds (70-85mph) and about 21 in city driving. And the EPA for my 350Z was 19/25, so obviously they under rated the mpg! And it seems the mpg is overly generous for the RX!
#76 of 96 Re: rx8 v 350z mpg [dat2]
Jun 11, 2007 (2:31 pm)
Two points you make; first, mpg. In commuting to work I normally get 19mpg--not great but not that bad.This includes stop and go driving using the freeway.Total freeway, the mpg increases to 21-22. My brother-in-law's infinity G-35 coupe gets about the same.Both cars are 2004 models. Very little difference here. As for lack of torque, the G-35 has about 100lb-ft more torque--yet he can't beat me in a race to 100mph.If torque is so important then why can't he beat me? The answer lies in the relationship between hp and torque. It is difficult to measure hp directly in a rotating device such as a engine,but measuring torque is straight forward.From this torque, one can convert it to hp.There is a math formula for this--but it is rpm dependent.Thus a car such as the rx8 that has low torque can have alot of horse power if it can have high engine revolutions.Thus at 8500rpm it generates about 240hp.So the reason I can beat my bother-in-law's G-35 is that I drive my rx8 at its hp max--that is 8500rpm.At this power max my hp to weight ratio is about the same as that of the G-35. So the bottom line is torque and rpm tells you how you must drive your car to get max power.
#77 of 96 Re: rx8 v 350z mpg [dat2]
Jul 14, 2007 (8:29 am)
dat2, the 350Z is a very nice car for people who like muscle car looks and ride, I could not sit in the 350Z on the race track for more than 20 minutes and my back was killing me, so I am not sure how long of a commute you can sit in the car without taking a brake. Now the 8, as comfortable as a Porsche, you can drive it for the full price you pay.
#78 of 96 Re: rx8 v 350z mpg [sssfegy]
Jul 15, 2007 (7:39 am)
Agreed, the Z is a track and highway racer. The RX-8 is usable even on really bad roads.
#79 of 96 rx8 vs 350Z
Jul 18, 2007 (9:20 am)
The Z has more power, the 8 has a better ride and a back seat. I haven't driven a Z, but I'm guessing the 8 feels much more agile due to a lower "polar moment of yaw" as one of the brochures puts it. Basically the engine is further away from the front end of the car, so it is easier to rotate.
The fuel economy/power output ratio of the 8 isn't that great, but the rotary engine has other benefits - smaller, lighter weight, etc. Plus you can rev it a lot without worrying about reducing its life, unlike a piston engine. Rotaries are designed to rev, in fact it is good for them.
#80 of 96 Re: rx8 vs 350Z [mdw1000]
Jul 24, 2007 (3:12 am)
My MPG has improved 20% since I bought my RX-8 AT new. After 30K I now get 17MPG in the city where a year ago I was getting 14MPG in the city. The first few months of ownership I was only getting 13MPG.
As for revving, there seems to be a quicker and smoother rise right up to the 7500 red line beep. It took at least a year before the full auto mode would reach red line to set off the beeper. It was a huge surprise the day it happened.
As for the 350Z's ride, I use to drive a consultant back to his hotel from work here in Boston. He owned a fully tricked out 350Z back in Arizona where he lived. Of my RX-8 AT he was very impressed with the rides ability to handle Boston's horrible streets. He concluded one would never be able to drive a 350Z in Boston without getting a severe back ache. He also said that he'd taken his 350Z on the track and averaged only 6MPG.
#81 of 96 Re: rx8 vs 350Z [trispec]
Jul 24, 2007 (10:17 pm)
Interesting. I know there is a saying that "a rotary's fastest lap is it's last lap." Apparently they have a reputation for getting better as they age.
#82 of 96 Re: The new federal millage rating system [trispec]
Jun 12, 2008 (12:59 pm)
My 2007 AT RX-8's best mileage was its latest fillup, 303 miles took 11.2 gallons = 27 mpg. This was from a daily commute of 30% suburban 10% urban and 60% traffic-jammed highway. The car just turned 7000 miles and has been averaging 25 mpg on this same commute, but I recently changed the engine oil from 15W-50 to 5W-40 which feels noticeably better (peppier).
I keep the tires at 40 psi but that doesn't explain why my mpg numbers are so much higher than the EPA numbers. I do avoid tailgating so in bumper-to-bumper highway traffic I am leaving a deacceleration cushion space ahead of my car whereas most drivers seem to be constantly riding their brakes. I am sure this practice helps alot since I am using the paddle shifters to slow down and I think the fuel computer shuts off the fuel injection during engine braking. Also, the AT drops into 6th between 40 & 45 mph and is geared so 60 mph is right at 2000 rpm.
I also use 1oz of Marvel Mystery Oil per gallon of fuel to help keep the engine innards clean but I doubt on such a new engine this will affect efficiency enough to notice.
So I am very happy with my RX-8's fuel economy numbers. I just wish Mazda could get those EPA numbers closer to my reality.