rx8daniel

I've found a way that 'may' be getting me 2-3% more MPG. The only way to tell is to get 5 or so other owners to try it out a couple tanks to see.
you'd have to:
1) have been checking mileage regularly
2) drive at least 10% 'city' type driving
3) generally drive at RPMs lower than 3K in during that 'city' driving

Here's the theory:
If you keep the RPM level in the 3250-3750 range as much as possible when under 65MPH. That includes cruising down a 2 lane highway like I do near my house at 55MPH in 5th gear. It doesn't mean to shift before 4K when accelerating to a faster speed, especially during heavy accel. It's difficult to learn to keep the RPMs up in that range during city driving. My normal cruising RPM had been around 2400-2800 as a guess. It's something I came up with after a few discussions at the Dragon this summer. I may be getting 21.7 versus 21 prior to this 'paradigm change'. I haven't driven enough since then to know though. Anyway - just PM me if you are willing to try it and let me know the results.

StewC625

Sure, I'll give it a try. I normally do this for cruising aroudn town anyway ... 5th gear on anything over 35 mph and 6th over 45 mph

Ike

Sounds like fun...

Tony Orlando

Look here to see how your test will turn out: 3250-3750 thread

I can't believe I beat him to this....

In honor of the digital ruler:

rx8daniel

I read the thread. I didn't see many answers. To say it a different way - I'm not asking anyone to change their shift points when driving - use 9K if you usually do, 3K if you usually do, just keep doing that the same. I try to redline at least once a day on the days I drive the 8. What I AM asking is that, for those that keep meticulous records AND usually drive under 3K RPM when 'cruising' - like at 35MPH in town or 25MPH in town, or 45 MPH in town, or even 55MPH on a highway (hopefully not in most towns) that they change just 1 thing - shift down a gear (or two) and keep the RPMs in that 3250-3750 zone as mentioned in the above thread. But again - keep revving for acceleration purposes the same. Continue to use 87 if you do already - or 91 if you do - or 93 if you do now. My problem coming up is 'winterized' blend will be hitting local stations within the next month and I may not get many miles in before the Miata goes back to the garageand the 'bland'er blend of gas.

Overport

why is everyone so obsessed with mpg's! its getting sooo annoying! who cares!

G8rboy

This has been discussed quite a bit- if you stay in that rev range (below 3750), you are keeping the secondary intake ports from opening up and guaranteeing better fuel economy. I do make an effort to stay in that band if I'm cruising at highway speeds, but in around-town driving, it's just too boring... the rotary was meant to be spun : ).

guy321

I don't think I can drive like that :D

Lets just hang out with our ***** out!

Twinturbo2800

......Well i 4 one care.


.....am i the only one who gets 200miles out of a full tank of gas (if im lucky!)
its rediculous, should i get it checked out by my dealer ??

G8rboy

I think many of us do- at least if you drive it like it was meant to. I usually get about 200-220 per tank (14-16mpg) in pure city driving, and 22-24 highway.

310Guy

I tried this "theory" with my auto; I used the paddle shifters and shifted EVERY time at 3k RPM for two tanks. It only improved my mpg by about 1.5-2 per tank. At the time I was getting about 12 mpg and it went up to about 14. BTW, I do about 80% city driving and have 7,500 miles on my 8 right now.

Razz1

Doooooooo

No fun, drive like a Grandma... Get a Bug!

Or better yet sell the car!

rx8daniel

I forgot to add in the original post... IF you don't care, don't read this thread. Don't comment. I don't care that you don't care. And to reiterate again (is the redudantly redudant?) I'm not talking about NOT trying to go 0-60 in 5.6 seconds from every stop light in town. IF your town has city streets with 55-65MPH speed limits (none that I've lived in- in IL, MO, TX, MD, or PA- has ever had that - Dallas comes close with many 45MPH streets) and you feel like acting like you are at a drag strip from every launch - that is fine. Continue the same thing. The only "change" [delta][variance][modification of driving style] (pick the word or phrase of choice) in anyone's fueling or driving habits is the RPM band when you are forced, by either speed limits or traffic, to maintain a fairly constant speed. And that change would be, if you are one that according to pre-PCM (harking back to ECU or even carb / points days) logic generally keep the RPMs lower in the 2000-2800 range. Again, continue to use the same fuel octane, same warm up, shut down, acceleration habits you always have. I'm suspecting there are few who qualify by keeping mileage records to begin with. If you don't - don't worry about it. If you don't care about mileage, you shouldn't have opened up this thread. I believe we get 300-800 posts a day - I generally don't open a thread that has an ambiguous title or has one indicative of a subject I don't care about. If you are still reading this and don't care about MPG, I'd suggest you consider the same! If you do care, and can help out, please do. If you care and can't help out, then subscribe to the thread and maybe read about comparisons if anyone can and does provider one or more before / after results. I will once I start driving the 8 more often. But... I don't do much 'in town' driving - my commute is 43 miles, of which only about 3 miles is non-highway. And for the record, when I drive in a spirited manner - say at the dragway or at the Dragon or even just redlining it at WOT when getting on the interstate - I don't care about MPG either. Those whose rear-end I had to keep backing off when I caught up with them again[at the Dragon] could attest to that.

rx8daniel

a thought to those who get 12 - 18 MPG: I don't understand the difference. I hope someday I can learn how one RX-8 can get 21MPG yet another 12MPG. Some of it can be attributed to driving habits, driving environment (city/highway/temperature/altitude/road conditions/etc), fuel qualities, maybe fuel brand, and several others. But not a 75% difference. Is it the ECU? Is it something in the drivetrain? Is it how 'tight' the engine is from the factory (compression?)? Is it something else in the fuel / intake / exhaust system - injectors, intake ports, exhaust ports? I would have returned my car last August instead of taking the free maintenance and the $500 debit card had I been getting anything < 18 MPG.
That said, I'm still wondering, whether you get 21MPG or 12MPG, if this one driving change helps MPG - again only if you are one that tracks it AND cares.

zevans

You should also try leaving more space / choosing a suitable lane / following phased stop lights so that you CAN spend more time at a constant speed. Example in my home town - there are three sets of lights in half a mile and most cars drive 0-30-0-30-0 between them. If you just drive through the whole lot at 20mph you save fuel.

It's all about area under the curve - if you draw a chart of speed versus distance your fuel consumption will be related to the area under that line.

My conclusion after 6000 miles in pretty much every condition you could hope to encounter - these engines just don't like speeds below 3000 revs, ever. The only time mine consumes oil is driving it proper hard for half an hour a so OR sitting in traffic all day. In normal driving it uses less oil than my TDI did.

In other words, I think you're right - and as well as following your advice you should maximise the opportunities to USE that advice. Try also to pick a gear which you can stay in without shuffling - which is often one lower than you use by habit.

Finally, don't drive over Gotthardpass in Switzerland - the combination of inclines and altitude did for about 10mpg... :D

G8rboy

I should have clarified that I have done this, and I do keep detailed mileage and maintenance records (every drop of gas and every mile driven). I can get approximately 2-3mpg higher by always settling my cruising RPM between 3250-3750 in my mostly city driving. I also did this on the highway on a weekend roadtrip, and saw an increase of 4-5mpg by staying in that range while cruising.

If you look at the Renesis' design with regards to intake tuning and fuel injection, this makes complete sense (which is why I decided to try this out myself)... 3750 rpm is the point that a lot more starts to happen.

rx8daniel

Appreciate that info. My low is about 18.3[winter], had one short tank that recorded 27.2 [7/24/03 with just over 1K on the odo] but otherwise my high is just shy of 24. My summer low is 18.7. I've had 4 tanks that were in the low teens but were at the Gap- although those are included in my overall average that is about 20.95. I don't expect even a 2MPG increase no matter what I do in daily driving. For me an increase of 4-5 would be significant. Hope we hear from others.

Feras

iTrader: (1)

a simple financial analysis:
average driver drives 12000 miles a year
extensive driver drives 18000 miles a year

combined worst mpg here are about 14mpg and best are about 22 mpg

the average driver with terrible mileage (using 93) will pay ~2.00 per gallon which ends up being a yearly expense of (12000/14)*2.00=$1714.29
if that average driver had great mileage he would pay (12000/22)*2.00=$1090.90

a savings of $623.39 per year for the 22mpg driver.

the 18000 driver with terrible mileage will pay (18000/14)*2.00=$2571.42 for gas
the 18000 driver with great mileage will pay (18000/22)*2.00=$1636.37 for gas

a savings of $935.06 per year for the 22mpg driver.

in both these examples the difference is 8mpg...if a modest (read: likely) increase of 2 or 4 mpg were expected then in the first example the savings go down to $156/year for 2mpg and $311.70/year for the 4mpg, and the same modest increase for the 18000 mile driver would result in a savings of $233.77 a year for 2mpg and $467.53 for 4mpg.

so what does this all mean...the benefits of driving this car like you would any economy car will result in savings of roughly 150-300 dollars ayear for the average driver ($12.50-$25 a month) and 230-470 dollars for the extensive driver ($19.16-$39.16 a month)

to me i find the sum of 40/month almost trivial, thats half the price of a nice night out...which cutting out 1 a month would be an easier prospect then not driving this car to the edge, the way it was bred to be driven. Personally i dont think the savings at the pump are enough to justify a change in driving style for me...gas just isnt that prohibitively expensive.

rx8daniel

Hi Feras...Daniel here...

everything you said makes sense. This all came from the discussion we had about this RPM range. the key is I'm not asking or even suggesting anyone drive their RX-8 like a Isuzu I-Mark diesel (anyone remember those - had a 0-60 time of about 18seconds) or even your average economy car. I'm not even suggesting anyone change their driving style. Only the RPM at which they do constant speed driving - which directly implies no change in acceleration or deceleration habits. I do my WOT or high % throttle driving exactly the same - I'm only changing from cruising at 35MPH from 4th to 3rd to hit 3500 RPM, or from driving 55MPH in 6th at 2800 +/- to 5th around 3600RPM (I can't remember exactly the diff).

guy321

You know what. I will open and post in any thread I please.

If you don't like mine or any other members comments, you can ignore them. This is a public forum. No one has been blatantly disrrespectful or disruptive.

Thanks.

Ninja

Personally I don't really care about the $$$ involved in gas mileage. This car is so fun to drive that WHATEVER it's costing me over my previous econo car is immaterial.

However, with the lower gas mileage, I do have to stop for gas more often which I just really don't like to do.

BUT, I believe I'm well compensated for the few extra minutes I spend gasing up every week. And no, personally, it's not worth it to improve the mileage and sacrifice driving fun.

RedRenisis

How bout this for an idea, maybe someone already said it, but I havent seen it so here you go

When driving around town, shift gears like 1st, 3rd, 5th, or 2nd, 4th, 6th, I do this quite regularly, no need to wind out all your gears when you could get by with just three, I do believe this could imrove gas mileage, but I have a very hard time keeping it under 6 grand, this car is just way too much fun, I agree gas hurts the pocket but what the hell, we bought sports car, they arent Honda's, think a Vette gets better mpg, think Vette owners care, I dont.

JeRKy 8 Owner

I have a feelingthat theres a different range for the automatic Rx8s b/c Ive tried this typeof bullshit driving before sinceIve had my car for over a year - and it doesnt help at all. Maybe the ports open sooner than 3750 on the automatic? Either that or it simplyhas no effect on my car. Every tank of gas thatIve tried this annoying experiment on -- Ive always obtained the samecity mileage whether or not I keep the RPMs under 3750.

Razpewton

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guy321

Just a thought, but if you DO try to change your driving patterns.. You should probably reset your PCM's learned settings either by disconnecting the battery for a minute or the 20 brake pump thing. Otherwise the PCM could be working against you.