RX8-CARL

Here is my strange observation:
Since having the new flash done the fuel gauge gets more miles for each 1/4 than it did before, 20 to 30 miles more, But the MPG is only up by at the most 1 MPG.
So is the fuel gauge run via the computer and changed to make you think you are getting more.

realdeal

I think because of the warmer weather your car is warming up faster, so your fuel efficiency increases. I too have noticed an increase in gas mileage, but I'm sure its a combination of warm weather and the N flash.

realdeal

I usually fill up and get 215-220 miles per tank. I usually fill up between 1/4 tank and empty. With the older flash i usually got 180-205 before i filled up.

mikeb

I was not trying to be rude
I just wanted some facts or answers why you think this happened

its kinda a huge difference

Fanman

Did you get a flash/service recently. Maybe it leaned out your A/F that should help with gas mileage.

papipito

Is no one even going to take a stab at this...30 mpg in CITY driving? That has to be sarcasm. You have to be pushing your car around the city.

I too, am appreciative of this thread. I think we all are a little confused with the whole gas mileage issue. There is no real rhyme or reason to it.

RX8-CARL

What I'm getting at is the gauge seem to show better economy than working it out shows.
With about 20 miles extra per 1/4 you would be looking at a lot more than at the most 1 MPG. I agree it seems to like warmer weather, but haven't had but a couple of warm days since November.

SilverEIGHT

I can compare my driving in two different RX8's. The first at 6,030 miles and the second one at 3424 miles. My driving style in both cars was pretty equal and I knew more about how to conserve on gas on the second car so that blows the theory about learning how do drive to conserve gas because my second one gets about 2 mpg less than the first.
============================
#1 - 04 Sport Pkg, 6MT - after 6030 miles my overall average mpg: 18.66
From May 04 to November 04
------------------------------------------------
1059 mi. 17.15 average mpg
2030 mi. 19.06
3050 mi. 18.69
4011 mi. 19.23
5122 mi. 19.03
6013 mi. 18.83

Highest mpg achieved: 26.78 (Interstate, 70 mph constant)
Lowest mpg achieved: 15.21 (Hard driving)

No break-in period. I drove like hell from day one.

============================
#2 - 05 GT, 6MT - after 3424 miles my overall average mpg: 16.88
From February 05 to May 05
------------------------------------------------
1083 mi. 17.16 average mpg
2201 mi. 16.77
3052 mi. 16.87
3424 mi. 16.73

Highest mpg achieved: 19.65 (Granny driving, first tank of gas)
Lowest mpg achieved: 13.94 (Mixed driving)

Break-in was the proper "don't exceed 400RPM for the first 1000 mi".

============================

I don't buy into the temperature theory as it has been to mild to claim that here in the Atlanta area.

PPen131

just playin around. i'm about to hit 200miles with a little less than a quarter tank left. all my driving on this tank of gas has been in stop and go traffic. it's been about 3weeks since i've filled up on gas because all my trips have been less than 10min(i've only been driving to and from the park and ride for work which is right by my house).

maikeru

I just went in for an oil change yesterday, and they flashed it. I had the M before so I'm assuming this latest one is the N flash since the tech told me it was newer than what I had. Too early to tell whether it's has affected my MPG good or bad.

LTABA

I've been getting two weeks out of a tank, but last month I drove the whole month with one tank! Do you think it's because of the new flash, or have I reached some sort of break-in milestone.?

P.S. I heard somewhere that you can actually calculate miles per gallon?? Does this take a lot of math skills, because I barely got through calculus.

Go48

Nah, i got a bunch of them calculus on my hands too and caint oprate the calcalator. Just figger the milage on ma toes.

RX8rider

Heres's for the math illeterate...just divide the miles driven (make sure to reset it to 0 at each refuling) by the amount of gallons you just filled up with. Example; 220 miles/13.5 gallons = 16.3 mpg.
Many people here have been dividing mile driven by 15.9 gallons (the size of the fuel tank) and that's wrong because you're not using the entire 15.9 gallons each time (unless you're a moron)

CowTownWoody

Back to the original question. Is there something about going for a long trip and running at high speeds for a couple of days (and high temp for hours at a time) that could cause better mileage in city driving upon your return? Could it clean some carbon deposits out of somewhere? Any theories? Maybe this should be a recommended monthly task for city drivers?

Go48

Look at it this way. When you are driving in stop-and-go city traffic, you spend a portion of the time not moving and, therefore, not racking up miles. So any fuel consumed when you are stationary is not contributing to your miles traveled. In a simple, extreme case, if you idled your car through a tank of fuel, you would get zero miles per gallon.

When you are on the open road and moving most of the time, you are racking up miles as you consume fuel.

CowTownWoody

Yeah, but read carefully. The original poster said that since doing this long road trip, his city driving mpg has improved significantly. The same stop-and-go city driving he was doing before the trip.

SilverEIGHT

As I stated above, my best mileage (26.78) was on the Interstate at a constant 70mph except for getting on and off to fill up. I was using the cruise control in the summer. My mileage never got better after that as you were asking, once back from the trip it reverted back to the same old mileage. Wish we could put our finger on the issue but I guess there are so many factors that we will never define it.

RPM's at shifting
Heavy foot
Flash version
Type of gas
Time of year
Altitude
Modifications

maikeru

RPM's at shifting= Usually at or before 3500 RPMs
Heavy foot= Sometimes
Flash version=Was M during Trip to Pa and back also for four weeks after. Got N flash on 5/4/05
Type of gas=shell or mobile 93 octane
Time of year=Now 50-65 degrees F.
Altitude=sea level
Modifications=none

My opinion is that that the PCM made some adjustments during the long trip which remained in effect until I got the N flash. I'm not through this tank yet but it looks like I won't be getting 250MPT as in my previous two tanks. My driving behavior has remained the same as always, but getting the N flash must have reset the PCM and now the MPG is lower. It looks a little better than when I had the M flash and was getting 180MPT but not as good as after the trip.

beefyjoe

I have to add my.02

160 miles to the tank. Stop and go. Brooklyn traffic. 12mpg is average for me. It sucks but I try not to think about it. 6spd, stock everyting, 2000 miles so far.