Last post on Jun 03, 2011 at 11:23 AM
You are in the Mazda RX-8
What is this discussion about?
Mazda RX-8, Fuel Efficiency (MPG)
#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.
#83 of 96 Re: The new federal millage rating system [avelectro]
Jun 13, 2008 (5:14 pm)
The new Federal standards match my normal MPG 15 City, 23 High Way. But if I drive to the Cape at 60mph cruise control, I get the 27MPG you get.
My RX-8 AT is mostly driven in city in manual mode in 2nd gear. 3rd and 4th would be dropping RPM's in down to 1200 where carbon build up is noticeable. I keep the RPM 2500-3500 in 2nd which covers all the city speeds up to 45MPH.
I saw a piece about an engine additive that kept rotor housing shiny sparkling inside.
#84 of 96 Re: The new federal millage rating system [avelectro]
Aug 20, 2008 (4:42 am)
avelectro wrote, "... is geared so 60 mph is right at 2000 rpm."
I wish the 6 speed manual's top gear was also such that 60 mph was 2000 rpm! In the 6 speed manual's case, it's 3000 rpm, so now I understand why the AT gets so much better mileage. My best recorded figure, to date, is 22.6 mpg. I'm working on trying to first get to the EPA published 24 mpg highway, and then I'll see what I can do to better it. I have heard of some manual RX-8s getting 27 highway; but I'm not yet clear on how it's being done.
#85 of 96 Any Owners of 2004 RX8s
Jan 13, 2009 (3:38 pm)
I'm being advised by a friend not to purchase the 2004 RX8. Can anyone who has owned a 2004 or older give me any advice about it? I really do like the car but don't want to make a big mistake..Gas mileage and oil don't concern me...I'm more concerned about the engine and finding someone to work on it should it need it.