Hello I have had my RX8 for under a month and I've been getting around 200miles for a full tank of premium gas. That's only 16mpg!!!!! I barely drive it hard, try to keep it under 3000rpm and never to exceed 4000rpm. I hear the manual guys getting around 18-20mpg. Arn't we suppose to be getting more mpg than the MT guys?

 

A well driven MT will always have a better gas mileage as an MT!
You have slip in the transmission and the transmission is harder to move and cost power and therefore gasoline! That’s the reason why AT cars are also not as fast as an MT. In the RX8 is also another problem present. It has only 4 gears! A bit more torque cannot fix the problem.

 

Hmm you have a good point but on the specs sheet, it says AT has a higher gas milage. I'm just wondering what other AT drivers are getting and what I should be getting.

Another thing is.. Most cars fall in the EPA range of mpg. However, I am no where near 18-25mpg.

 

Not true in this case. (And for some cars the ATs are just as fast as the MTs, mostly high torque V8s)

The 8's AT is geared much higher than the MT. Cruising at 80mph in the 6spd puts you at almost 4000rpm, while the 4AT puts you at 3300rpm. I get 18-20mpg city, 23-27 highway depending on speed.

Your gas mileage depends heavily on cruising rpm. Transient rpm means little, as you only rev high on acceleration. Slip only occurs on acceleration. The transmission goes into lockup at cruise, meaning it's directly coupled to the engine. Keep an eye on your cruising rpm and gear. I'm willing to bet your using 2nd and 3rd gears alot more than you have to. 95% of your driving will be done at cruising speed.

And rev that engine. You need a redline every now and then to keep carbon from building up. Carbon buildup will be detrimental to power and mileage. I redline multiple times a day, but in traffic I get to 4th gear as soon as possible. Try reseting your ecu (there's a thread in the tech forum), and changing your driving habits to using one gear higher than you usually do for certain situations. I'd put money on better mileage.

Lots of idling and short trips when the engine is cold will cause lower mileage as well. The car burns alot of fuel when cold.

 

My car is only at around 600miles so I dont think I would need to clear the carbon. And no I drop to 4th gear at around 40 mph, my car pretty much skips 2nd gear. I'll change gas and see what happens. I will switch from premium costco gas to maybe 89 shell gas.

 

I'm getting around 13.8 mpg driving in city traffic w/AC on... I got stuck in mad traffic one day for about 2hrs... got 10.2 mpg on that tank, so your doing better than me...

 

14.9 MPG give or take, 90% city driving, I pretty much have never gone over 15 since getting the car a year ago. I drive 100% in the manual shift mode, rarely ever use 4th gear because anything below 50MPH and the car starts bucking like a bronco (likewise with 3rd, anything below 35 and the car feels like it's going to die a horrible death). But ever since hearing about the carbon build up problem, I have been doing a lot more 5k RPM runs in 1st and 2nd whenever I can, which probably ain't helping the MPG. But whatever, I wasn't expecting great MPG when I bought the car, as long as I don't drop below 13, I'm happy.

 

That just sounds ridiculous. I use 4th down to 21mph with no problems. Sure you can't accelerate much, but that's what the shifter is for. But hey it's your mpg. Use 4th to cruise and not to accelerate. Though mine accelerates just fine in 4th at 50mph in traffic. Either you're exagerating or there's issues with your car.

 

Let's say you're driving 30mph for some reason, what gear are you using? I use 4th.

 

I am getting 21-22 mpg with my A/T

 

I have an MT and get 21-23 MPG, Country road driving. I never run UNDER 3,000 rpm's, shift around 5,000 -6,000 rpm's in lower gears and while cruising in higher gears I downshift to stay above 3,000 rpm's. Going up the mountaian I cross I keep it around 4,000-4500 rpm's. The Rotary is bogged down under 3,000 rpm's the only time running at that low of rpm is practical is while going downhill. The best gas mielage is obtained when we are using the gear that will maintain the desired speed with the gas pedal depressed the least. I use 87 Octane Shell.

 

Nope, not exaggerating at all. The car lugs horribly at those speed/rpm combos I mentioned. I'm not the only one with this problem either. I've asked about it in the past and some have attributed it to the rotary's lack of low end torque, but nobody ever gave me a solid, definite reason as to why I might be getting such lugging in an automatic. Last time I mentioned it to the dealer all they told me was "oh it's probably in too high of a gear".

 

That shouldn't be happening. Mine cruises fine in 4th down to about 25 MPH. Like therm8, if I need to accelerate from low speed, I'll downshift (I typically drive in Manual Mode). But I've NEVER felt the engine lugging like an MT car in too high a gear.

 

I get an average of 260 miles per tank.

 

Hmm.. when did you buy your 8 and what was the production date? (Same question goes to all AT drivers who have around 20mpg)

And yes normally if cruising at 30mph I'm at 4th.

 

I read in the owner's manual that you're only supposed to use 87 octane...is that true? Or does premium gas give it a little more oomph? It says that maximum performance comes from regular, but that just doesn't make much sense to me...anyone have any insight into this?

 

um you should read that page a little closer=) because mine says 91 octane is best for it. performance wise.

 

built Jun '03 purchase Nov '03, currently 48000 miles. still on L flash. Perhaps your just getting break-in mileage, though I've always had relatively good economy. Do you do alot of idling at stoplights? Short trips?

 

My bad, you are absolutely right, 91 octane is the recommended fuel...haha I'm stupid, I thought I read "regular unleaded" for some reason...sorry about that

 

Do a search on octane ratings and the effects on the 8.

 

Well yes my trips are considerably short, however how might that have an impact on fuel economy? Break-in mileage is what I was thinking. (Friction in engine during break-in uses more fuel.. right??)

 

Well, the car burns considerably more fuel during its warmup than at any other time. If a majority of your driving time is spent in this warmup period, then your average will be lower. This is probably the culprit. You could see some improvement with some more miles on the car.

 

hmmm maybe a gas saver would be to let the car warm up before driving its worth a shot!

 

Mine is an 04 AT with 7000 miles.
91 Octane with a 200:1 pre-mix,
60 second morning warm-up's,
90% City under 40mph (mostly in 2nd gear)
10 minutes from work.

My "wonderful MPG = ???


Never more then 12 MPG...


I'd love to get your "bad mpg"


Did I mention I have a Silver 8 ?
(?Curse?)

 

And AT 6CYL Supras