I'm only getting 15mpg city, is this normal? j/k.

I figured I'd consolidate some tips on improving gas mileage in this thread. I know people are sick of talking and hearing about gas mileage, but I figured this might be ok since it's more like driving tips.

So, I was getting ~16mpg mixed driving. Now I'm getting close to 18 mpg mixed driving (17.5-18.25). At least this is what I got on my last 3 or so tanks. This is what I do now:

1) I don't let the engine warm up. I wait for the engine to "settle" then leave. "Settle" means I'm around 1.25-1.5K rpm. (Advice from the manual)

2) When the engine is cold, I shift around 2.5-3K rpm. (Supposedly the engine uses double the gas when its cold? I think I heard that somewhere)

3) When coasting I leave the car in gear until I'm close to stopping, then I put it into neutral. (Supposedly the engine uses NO gas when coasting in gear I think. At least I read that somewhere here I think.)

4) When the engine is warm, I shift around 3.75Krpm, but I'll push it when I feel like it. I usually bring it up in the higher revs (7K+) at least once whenever I drive. (The second fuel injector starts working at 3.75K). Also if you're on a freeway try to keep it under 74mph (under 3.75K rpm).

5) I get into 6th gear the second I hit ~45mph and don't need to accelerate very much more. So if I'm in a 50mph street and there's cars in front of me, when I hit around 45mph, I'll change to 6th. But if I'm getting on the freeway, I'll shift however I want to shift, I just make sure I'm in 6th as soon as I'm done doing the bulk of my acceleration. I'm guessing this is probably the biggest reason for my mpg improvement.

<new recently added ones on edit>
6) Avoid idling. Idling = using gas, yes it is relatively minor but you're using gas and going no where.

7) Avoid shutting off and turning on the engine multiple times in a short span. This also means avoid many short trips. If you're making a lot of short trips and the engine doesn't get a chance to warm up, your mileage is probably going to suck.
</new recently added ones on edit>

Previously I was doing just doing tip #1 and shifting around 3.75K rpm all the time. I put the car in neutral a lot too when I coasted. Keep in mind that I also got better at driving manual but I did get a marked improvement (almost 2mpg!) since changing my driving habits a bit.

I also use Shell 91 octane. I tried 87 once and I thought I was getting better mileage for the first half tank, but then it wound up being the same as I get with 91 by the end. Oh and for other stats; I have a Grand Touring, 6 speed manual with about 7000 miles on it.

Anyone else have any other tips?

Have you gotten the latest "N" flash. People who have gotten it have said the fuel mileage is a bit better.

1) I don't let the engine warm up. I wait for the engine to "settle" then leave. "Settle" means I'm around 1.25-1.5K rpm. (Advice from the manual)

2) When the engine is cold, I shift around 2.5-3K rpm. (Supposedly the engine uses double the gas when its cold? I think I heard that somewhere)

3) When coasting I leave the car in gear until I'm close to stopping, then I put it into neutral. (Supposedly the engine uses NO gas when coasting in gear I think. At least I read that somewhere here I think.)

4) When the engine is warm, I shift around 3.75Krpm, but I'll push it when I feel like it. I usually bring it up in the higher revs (7K+) at least once whenever I drive. (The second fuel injector starts working at 3.75K)

5) I get into 6th gear the second I hit ~45mph and don't need to accelerate very much more. So if I'm in a 50mph street and there's cars in front of me, when I hit around 45mph, I'll change to 6th. But if I'm getting on the freeway, I'll shift however I want to shift, I just make sure I'm in 6th as soon as I'm done doing the bulk of my acceleration. I'm guessing this is probably the biggest reason for my mpg improvement.


1) i don't even wait that long usually. i'll just crank it, put my seatbelt on and i'm off. i think the rpms are still around 2.25k when i start out. and for those that wait for the car to warm up before driving, easy driving is the quickest (safe) way to bring the engine to temperature, and it doesn't kill your fuel economy.

2) i never take the engine above 3k before its up to temperature. it does run rich right after cranking, but i don't know about double the fuel, but then again i haven't gone out and measured it either.

3) yup, when coasting the car is in DFCO (deceleration fuel cut off), and uses no fuel...the momentum of the drivetrain keeps the engine spinning. if you are in neutral the only way to keep the engine spinning is if fuel is being injected.

4) i typically shift between 3k and 3.5k rpm in normal traffic driving. but when having fun, i'll take it all the way up to redline. and its the 2nd intake ports that open at 3.75, not injectors. only one set of those per rotor, iirc. ;)

5) unless i'm going up a hill (which there are lots of around here), then i'll usually go into 6th somewhere in the 40-45mph range.

about the only thing that i do that you didn't mention that i do is keep it at 73mph or under while on the highway to keep the secondary intake ports from opening. and i've averaged 18.351mpg over ~2000 miles and 2 months.

I think all the tips are good ones. I may get 18 mpg when I follow them, or 16-17 when I drive to have fun. The 1-2 mpg I lose by having fun increases my fillup cost by $1.00-$2.00. I fill up about once a week, so the total extra is $100 a year. If I wanted to save $100 a year, I wouldn't have bought the 8 to begin with.

Life is too short. I won't let obtaining maximium mpg dictate my driving style, but I will keep the tips in the back of mind.

oh, believe me, i have fun in my car; i typically hit at least 8k once a day, and have stepped the backend out more than a few times. but when you are sitting in traffic, there's no need to run out each gear. so by maximazing fuel economy in traffic, i have more fuel to play with when the opportunity presents itself.

4) i typically shift between 3k and 3.5k rpm in normal traffic driving. but when having fun, i'll take it all the way up to redline. and its the 2nd intake ports that open at 3.75, not injectors. only one set of those per rotor, iirc. ;)
No, there's an injector intake runner. 2 per rotor for the low power, and 3 per rotor for the high power.

I used to follow all these driving when I first got my car. I was getting 18-19mpg. I'm down to about 17 right now, but I've been being more agressive recently. Guess sometimes that mood hits...

--Massive

Have you gotten the latest "N" flash. People who have gotten it have said the fuel mileage is a bit better.

Here we go again with the flash bullshit. Anytime I ever upgraded to another flash on my last RX-8, my mileage just kept getting worse. If it ain't broke don't fix it.

No, there's an injector intake runner. 2 per rotor for the low power, and 3 per rotor for the high power.

I used to follow all these driving when I first got my car. I was getting 18-19mpg. I'm down to about 17 right now, but I've been being more agressive recently. Guess sometimes that mood hits...

--Massive

could have sworn i read someplace that there was only 1 injector per rotor that supplied all 3 intake ports. guess i was wrong.

Spork, I think that you have just described the way that the 8 is supposed to be driven and what you are saying reflects closely what the manual says to do. Good for you and good post. I also think that it would be difficult to overestimate the amount of fuel that the 8 uses when it is running on choke during the warm up period. The less time that it spends idleing during this period the better, and that means starting and driving right away, conservatively as you describe, until warm. This also reiterates what Mazda has been saying all along. The only other thing that I might suggest is that if the car is driven hard or in city traffic a lot, to check the spark plugs earlier that Mazda suggests. I gapped mine in at 27,000 miles to the close end of the gap range (they were actually beyond the range at that point in their lives) and the power in my car and fuel mileage both increased. Enjoy those 8s. - H

I've a wide open 20 mile commute in the AM and a clogged 20 in the PM. 10 plus tanks of gas and 2700 miles driven. Lot's of trips to 9k, lots of spirited driving, reluctant to place in 6th. Best mileage on a tank 23, worst 19. I shift when I want, not per the book and have fun with it where I can - on-ramps, off ramps. I had prepared myself for poorer mileage but so far so GOOD.

3) When coasting I leave the car in gear until I'm close to stopping, then I put it into neutral. (Supposedly the engine uses NO gas when coasting in gear I think. At least I read that somewhere here I think.)


I do everything you do except #3 and I'm still getting about 15 MPG. I tried tip #3 recently (three tanks worth) and I'm using MORE fuel than coasting with the clutch in.

try adding intake/exhuast, should help if you leave you lead shoes as home

3) yup, when coasting the car is in DFCO (deceleration fuel cut off), and uses no fuel...the momentum of the drivetrain keeps the engine spinning. if you are in neutral the only way to keep the engine spinning is if fuel is being injected.
I thought the engine doesn't spin when you're in neutral. Aren't the RPMs at 0???

I do everything you do except #3 and I'm still getting about 15 MPG. I tried tip #3 recently (three tanks worth) and I'm using MORE fuel than coasting with the clutch in.
That sucks. Well, all I know is after I added the coasting in gear and the get into 6th ASAP, I got about 1.5-2 mpg more than I usually did. I tried it for a few tanks and I don't get under 17mpg now (17.5-18.25) mixed (about 30-40% freeway) where as before I got around 16 (16-16.5 mpg).

The way I figure it is if you don't get at least 19mpg going 80%+ freeway (non stop and go) then your car is defective. Even when I was getting ~15 mpg mixed I jumped to just over 19 mpg when I did a roadtrip to San Diego which meant I did something like 70% freeway. There's not much you can do that's wasteful when doing a lot of freeway driving unless you're constantly gunning it to pass people, in traffic, or not in 6th gear.

I still have yet to break the 20mpg barrier though.

I thought the engine doesn't spin when you're in neutral. Aren't the RPMs at 0???
No, the RPMS on my car are around 750-900 rpm when I'm in neutral and the car is warm.

about the only thing that i do that you didn't mention that i do is keep it at 73mph or under while on the highway to keep the secondary intake ports from opening. and i've averaged 18.351mpg over ~2000 miles and 2 months.
I try to do this but I just can't most of the time. I'm usually going high 70's on the freeeways unless there's traffic.

I got 12.25 mpg on my last tank of gas. I'm not a lead foot either. I didn't autocross on this tank. I'm doing all of the things in post #1. All city driving though. Virtually 0 highway.

I got 12.25 mpg on my last tank of gas. I'm not a lead foot either. I didn't autocross on this tank. I'm doing all of the things in post #1. All city driving though. Virtually 0 highway.

Are you still up in Dallas, or is that tank from in Houston? I get around 15-16 here. I usually avoid the highways as most of my driving would be on 635 going the wrong way each way. If you're idling a lot with the A/C on, your mileage will suffer quite a bit just from that.

No, the RPMS on my car are around 750-900 rpm when I'm in neutral and the car is warm.I guess that makes sense....0 RPMs means the engine is dead/off ;) :o I'm a dumbass.

Are you still up in Dallas, or is that tank from in Houston? I get around 15-16 here. I usually avoid the highways as most of my driving would be on 635 going the wrong way each way. If you're idling a lot with the A/C on, your mileage will suffer quite a bit just from that.

Nope, this is Houston driving. Lots of sitting in traffic/idling. It was at the dealer with this tank of gas so they might have left it running in neutral or something for an extended period of time. I've already got more miles on this tank than the last tank, so I know that the mileage will improve, but it doesnt look to be a drastic change.

Last tank was 152 miles / 12.4 gallons, yielding 12.25

Depending on what it was at the dealer for, they may have idled it for an excessive amount of time. I know when my wife takes a long time to leave work, my mileage suffers as I wait for her after leaving my building.

I added these:

6) Avoid idling. Idling = using gas, yes it is relatively minor but you're using gas and going no where.

7) Avoid shutting off and turning on the engine multiple times in a short span. This also means avoid many short trips. If you're making a lot of short trips and the engine doesn't get a chance to warm up, your mileage is probably going to suck.

and i changed #4 a bit to reference the fact that you should try to keep it under 74mph in 6th gear when on freeways.

for me, AC doesn't seem to affect me much, but then again I use it sparingly so that's probably why i don't notice any effect.

i think my a/c has been off once in the past month and a half. i'd say it isn't really affecting my mileage much, but i don't have much no-a/c driving to compare it too (had the car for slightly less than 2 months).

short trips and frequent shutdown/startup is a MAJOR fuel efficiency killer in a rotary. Quite a bit of fuel gets dumped into the housings during startup.

A better way to save gas would be to sell that pos and by an STi

Stop trolling and change your screen name. You were already asked once.

I am averaging around 19.8 MPG, and as far as the STi comment above if I wanted to buy an over priced civic look alike with a craptastic looking exterior and the super basic interior I would of picked one of those up. Considering that people's reaction to the RX8 is one of pure envy, just curious what it must be like when people look at your Sti and wonder why someone would drive something that looked like a freakin turd on wheels.

I just filled her up, went from 12.25 to 13.8. I'll be driving to Matagorda Bay and back in the next few days so hopefully I can see what 6th gear will yield.

Personally, I never shift into 6th gear unless I'm on the open road running around 70 mph. I try to stay in the 3,000 to 3,250 rpm range when cruising secondary roads, etc. This engine is happiest when revving. It is not always like driving a conventional piston car. Due to lack of torque, the computer will dump extra fuel to try to compensate when bogging around at 2,300 rpm in 6th gear if you accelerate at all. I have right at 20,000 miles and always get around 18.5 mpg (50 / 50) regardless of driving style. This was discussed in depth when I first started reading this forum and has stuck with me. It works for me.

HD

Since the N flash I have gotten 18-20 avg. Doesn't matter whether I baby it or get on it. The only difference I see is hywy vs. city.

I was getting 16-18 before w/ I believe the buggy M flash.

Gas mileage in by opinion has not been too bad with this car. The lowest I got was 16.5mpg (Hard Driving), The highest was 20.5mpg (Tried to drive easy the whole tank but couldn't resist opening it up a couple of times). I pretty much do everything in the original post with a couple exceptions.

Scenario: Cruising at ~55-60mph in 6th gear, want to accelerate to pass / change lanes.
Shifting: Downshift to 4th get to desired speed, shift back to 6th.

I don't know if this is what a lot of you are doing and I don't know if my thinking for doing this is right. But wouldn't accelerating in 6th gear actually use more fuel than downshifting to a lower gear. High throttle position inputs in a high gear will make the engine work hard. In the lower gears the engine does not have to work as hard due to the gearing of the tranny. Isn't this the whole point of the transmission anyways?

My thinking: Putting the pedal to the floor in 6th at 55mph will use more fuel than briefly downshifting to 4th to accelerate to desired speed. (It's quicker too)

I've stopped tracking gas mileage. It wasn't easy for me to do. I do not reset the trip meter. I do not try to register in my brain what the odometer or trip meter shows when I fill up. I know have no idea how many miles/kms I get per tank. I'm enjoying the car much, much better !! I'll probably start tracking again in another 10,000 miles or so (and probably just for a few thousand miles) just to make sure everything's still ok.

Scenario: Cruising at ~55-60mph in 6th gear, want to accelerate to pass / change lanes.
Shifting: Downshift to 4th get to desired speed, shift back to 6th.
Oh, I downshift if I need to pass. If I'm going 45 in 6th, it's really hard to pass people. I'm just saying that if you don't need to accelerate quickly, get into 6th and stay in 6th ASAP. It worked very well for me. Tt was either that or the coasting in gear, or both which helped bring my mpg up rom 16-18.

I don't think it's that bad to go to higher rpms, provided the bulk of your time is in 6th gear and below 3.75k rpm.

I try to stay in the 3,000 to 3,250 rpm range when cruising secondary roads, etc.
Doing the keeping the rpm between 3-3.25 is pretty difficult. It's really easy to be above/below that unless there's no lights and the streets are empty. I tried keeping it between 3-3.75 before and my mileage still stayed around 16mpg.

but wouldn't accelerating in 6th gear actually use more fuel than downshifting to a lower gear.
i'm not sure, but i don't think it would. not positive though so if someone really knows the answer to this, it'd be nice to know the answer.

I just filled her up, went from 12.25 to 13.8. I'll be driving to Matagorda Bay and back in the next few days so hopefully I can see what 6th gear will yield.
If you don't get at least 19mpg on a trip where it really is 80%+ in 6th gear without varying your speed too much (and usually under 74mph), then there is something wrong with your car. There's not much "wrong" you can do driving once you're in 6th gear and cruising where as there can be a lot wrong when you're driving city streets. But then again I don't know if they'll do anything about it. A member here, Howard, got the same mileage as you and he eventually took it in to the dealer and had them test the mileage and they got the same as him (~12). I don't think they did anything for him yet though.

I do everything in this thread, for the most part, and I average 19 MPG. Most of my driving is to/from work and is about 60/40 c/h. This last tank was 19.2 and it was mostly highway, except I was toying around for some time and above 100MPH for a while.

My typical shifts leaving lights are either 1-2-5 (for speed limits 35-40) or 1-2-6 (for higher speed limits). Out of my 1-2 shifts, I'd say 85% are at 5-6k. 10% are above 6k and the last 5% are under and only done when the speed limit is really slow. Furthermore, most of my 2-6 shifts on high speed roads are in the 5-6k range or higher too.

I dunno, the way I look at it, the faster I can get to a coasting speed, the less overall gas I use. And, given my 19MPG average, I guess I'm not too far off.

edit: my highway cruising speed (as per the speedo) is generally 75 if I can do it with the surrounding traffic (which is often).

Haven't done the calculation but it is much worse than my previous car ('01 BMW 530i). I have a 40-45 mile commute to work each way. Currently spending about $12 a day for fuel ($2.00 to $2.30 a gallon for premium). I figure I'm using about $60 a week. I was using about $40 - 45 a week with the BMW.

BUT, I don't care. I knew the car got crap fuel mileage. I think even my '05 X5's mileage is better. I bought the car for fun so I'll just have to live with the fuel cost. If fuel hits $4 a gallon, maybe I'll buy another BMW or Audi to commute with and keep the 8 for fun. Until then, I'm having a ball with the new toy.

I do everything you do except #3 and I'm still getting about 15 MPG. I tried tip #3 recently (three tanks worth) and I'm using MORE fuel than coasting with the clutch in.

I coast in neutral clutch out ... Do I save just as much as coasting with it in gear?

I averaged about 21.5 on the highway, cruise set at 80mph. In town, I have been averaging about 19-20 mpg. This is with a 6mt and very varying driving habits.

^^ about the same here. I got tired of tracking mpg stats and figured I'll have to fill up regardless anyway so why bother? And most of my driving is city and very little, IMO, can be done to help me there.

Those are great tips, but I think it also goes to show how unique our cars are. Last Friday, I filled up and then took a trip up the highway running about 75-80 mph and passing a few cars along the way. I was following a friend in a Cavalier btw. He drove the crap out of that car. Then we started up a twisty mountain pass, going from about 6000' to 8800', running high revs and driving hard all the way up and back down. Then we opened it up for the duration of the trip, running about 85 and passing cars, hit a high of 96 for a brief period of time. The trip back home was much the same, but probably not quite as fast. Round trip was probably about 175 miles. Then I drove the rest of the week back and forth to work as usual. I just filled up again today (the fuel light came on). I had 289 miles on the trip meter, and it took 13.9 gallons. 289/13.9 = 20.79 mpg. I haven't had the opportunity to run a full tank of gas on a freeway, but I suspect that I would get somewhere in the 23-24 mpg range. I feel for those that are getting crappy mileage.

If I wanted to follow the tips on the first page, I wouldn't have bought an RX-8.

6th gear at 45? I'm usually in 3rd. Shift at 3k? When I short shift, it's at 4k. Regular shifts are at 6k or above. With the occassional redline shift also. What's the point of buying an RX-8 if you aren't going to DRIVE it.

I figure it's worth the 1-2 mpg to have fun in the car.