canzoomer

I suggest you ask at what rpm do you normally shift in 1st, 2nd, 3rd.

canzoomer

If a person has been recording use in highway and city driving reasonably accurately it is easy to see the difference to a great degree.
Here are my stats. I live in Alberta, we have some long open highways, and most often run at around 145kmh (90mph) at around 4300rpm on the highway.

Based on my last 12 tankfuls, I had 7 of mostly or all highway and 5 of mainly or all city.

I averaged 14.43l/100km, or 16.37mpg on highway
I averaged 17.07l/100km, or 13.80mpg in city.

8_wannabe

That's question 3, driving style.

8_wannabe

I find it interesting that most people apparently think they either drive more than 80 percent highway or less than 20 percent hiway. This is a phenomenon known as a "well curve" that goes down in the middle. If it were a bell curve as I would have expected, most drivers would say they are around 50/50 hiway/city, and it would tail off at both ends of the curve.

RX8by

18.9 mpg
50%
B
108393
GT
6 Speed
93 of **** poor ethanol made for smog control can't wait for the winter version
Yes
1989 mileage
0 % windows
5 % AC
ILL

Just a note mileage last 4 tanks hasn't varied more then + - .3
I had the tires at 40 psi ( first 600 miles ) didn't check the dealers work, but I was getting 21 mpg. The ride was a rough one. I am going to try 35 psi. I found my Tundra gets better mileage 2-3 mpg by running 32 psi vs the recommended 28 psi.

norton

RodsterinFL: That's terrific! How did you get this info so quickly. Do you have navi, and if so, is avg speed displayed??
If we could get that info (avg speed) from everyone, that would be great. I believe Avg Speed is a much better determinant of MPG than % Hwy, which is really only a ballpark estimate.

RodsterinFL

I know exactly how far my work is. I have driven there for 6 years. Basically I figured average travel time with miles traveled. The time was easy for me to figure since I look at the clock each morning and then write in my arrival time at work each day.

MPG > HP

Seems like avg. MPH would yield the most normalized result. Trip lenght might help, as well.

VIN 108802 Recent MPG at ~5k odo = 21.1

MPG > HP

Here's info, as requested:

1. RECENT Combined City/Highway Average MPG = 21.2
2. % Highway Driving =85%
3. Driving Style = ? econodrive w/ 2 sprints to 9k
4. VIN Number (last 6 digits) =108802
5. Model (eg. Base, GT, etc) = GT
6. Automatic / 6 speed = 6 speed
7. Octane (Number) of Fuel Used = 87
8. DSC/TCS = Yes
9. Miles to Date = 4,892
10. Approximate % Time Driving with Windows Open = 1
11. Approximate % Time Driving with AC on = 100
12. State = SoCalif

norton

MPG > HP: I couldn't agree with you more. The problem is obtaining it is somewhat a pain. In addition to the odometer reading, everyone would also need to record the cumulative driving time (over the same period for which they which they are also calculating MPG).
If people did this, then we would have some GREAT data to work with. If anyone is interested in pursuing Avg MPH please let me know. I would do the calculation if you provide the Cumulative Time.

MPG > HP

Ok, anyone wanting to participate would need to follow a procedure, like this:

1. Add an "Avg MPH" column to your MPG Log. (Keep "Trip Times" on a separate scatch sheet).
2. Always log start and end times so trip times can be calculated.
2. At each fillup, add all the trip times since the last tankful and divide the total trip miles by the cumulated # of hours for Avg MPH.
3. Report your mileage and Avg MPH here.

As long as you can get good numbers for any given tankful it won't matter if you "mess up" logging for any "MPG Only" tankful. Accuracy would count more than quantity of sample points, so if you can only report MPG, that statistic would be usable, as before.

If you wanted to be really accurate, feel free to add a "Trip Miles" column. I'm sure Norton can separate out the reports of "MPG", "MPH" and "Miles Per Trip", but you would have to keep accurate per trip logs to get the benefit of really accurate numbers. This would especially show the difference between open hiway, rush hour and short city trips where the most variability is likely to occur. ("Stomp the gas" trips could be asterisked, if you really want to go crazy on this.)

I'll start logging for avg mph at the start of my next tank and see where this takes us.

norcalrx8

1. 19.8
2. 80
3. Average,
4. 107556
5. GT
6. 6 speed
7. 89
8. Yes
9. 2950
10. 50
11. 50
12. CA

Charles Cope

1. 17.4
2. 70
3. C
4. 100502
5. T
6. 6 speed
7. 92
8. Yes
9. 4666
10. 2%
11. 2%
12. MI

bobclevenger

OK, I just got my 8 two days ago. Here's the results of my first fill-up. I'll try to post new data for each fill-up (unless I'm away from my computer at the time).

1. RECENT Combined City/Highway Average MPG = 18.8
First tank. Dealer fill-up.

2. % Highway Driving = 60%
3. Driving Style = A I'm still in "break-in" mode.
A. Easy going (Don’t normally use high rpm range, only occasionally)

4. VIN Number (last 6 digits) = 107141

5. Model (eg. Base, GT, etc) = GT

6. Automatic / 6 speed = 6-Speed

7. Octane (Number) of Fuel Used = 91 (dealer-supplied)

8. DSC/TCS = Yes

9. Miles to Date = 294

10. Approximate % Time Driving with Windows Open = 0

11. Approximate % Time Driving with AC on = 2

12. State = Calif.

Microbe Hunter

1. 16.45
2. 63%
3. B
4. 111534
5. GT
6. 6 speed
7. 93
8. Yes
9. 538
10. 10%
11. 60%
12. Alabama

Local conditions in city driving involves hills and many short runs with stop signs.

8_wannabe

Hey Norton, how about an updated chart like the one you did on 10/24. You've got a lot more datapoints to include now.

Buger

I'd like to thank Norton for bringing a statistical approach to the fuel economy issue. It's always nice to see practical application of an education.

The RX-8 would not have made it to production if it couldn't pass the gass guzzler tax limit which is 22.5 mpg (unadjusted combined).

The results of the EPAs tests were seen briefly on Mazda's website and caused some initial high hopes. Does anybody remember what they were?

20.4 mpg city / 30.2 mpg highway

The EPA's numbers were actually 20.402 mpg city / 30.2244 mpg highway (23.8967 mpg combined). These EPA unadjusted figures are determined by running 2 driving schedules on dynos. To test city/urban economy, the EPA measured fuel usage on their LA-4 driving schedule (aka FTP-72, UDDS, etc). To test highway fuel economy, the EPA measured fuel usage on their Highway Fuel Ecomony Test (HWFET) driving schedule.

So how did the numbers change from 20.4/30.2 to 18/24? Sorry to proponents of conspiracy theories but www.fueleconomy.gov has the answer:

"To make the numbers in the Fuel Economy Guide more useful for consumers, EPA adjusts these laboratory test results to account for the difference between controlled laboratory conditions and actual driving on the road. The laboratory fuel economy results are adjusted downward to arrive at the estimates in the Fuel Economy Guide and on the labels seen on new cars, light trucks, and vans. The city estimate is lowered by 10% and the highway estimate by 22% from the laboratory test results. Experience has proven that these adjustments make the mileage estimates in the Fuel Economy Guide correspond more closely to the actual fuel economy realized by the average driver."

20.402 * .9 = 18.4 city mpg
30.2244 * .78 = 23.6 highway mpg

How many people here knew that that? The EPA verifies their above preproduction testing results on 10 - 15% of the production models.

There are many factors which can affect individual fuel economy but if anyone here doubts the EPA results, they should be able to find a certified testing center that can simulate the FTP-72 and HWFET dyno tests under federal testing conditions.

Brian

RedJade

1. MPG: 18.62

2. % Highway Driving = 85

3. Driving Style = B: Average

4. VIN Number (last 6 digits) = 103488

5. Model (eg. Base, GT, etc) = GT

6. Automatic / 6 speed = 6 Speed

7. Octane (Number) of Fuel Used = 92

8. DSC/TCS = Yes

9. Miles to Date = 1700

10. Approximate % Time Driving with Windows Open = 0 %

11. Approximate % Time Driving with AC on = 80 %

12. State = Missouri

norton

I'll try to do an update on the MPG analysis next week. Been swamped lately with my job.

Reeko

I wish we had a way to track another factor... Average Temperature.

I have mentioned in another thread, but my MPG dropped by about 2MPG consistently when the average temps around here dropped from mid 60s to upper 30s (we had a sudden cold spell for 2 weeks). I went from a consistent 17 MPG down to <15 MPG (the 15 was over 2 tanks).

Interesting also is the fact that the temps are warmer now, and I can tell that my MPG is back. I haven't finished a tank yet, but during the "Bad" days, I went through 1/2 tank before I hit 100 miles, my current tank hit 1/2 at 125 miles (I am at 176 miles at 1/4 tank now, typical to my 17 MPG tanks).

pcorsaro

I posted my data before, this time with your from.

1. RECENT Combined City/Highway Average MPG = 14.7
(Calculated Correctly and One Number please, not a range)

2. % Highway Driving = 85%

3. Driving Style = C
A. Easy going (Don’t normally use high rpm range, only occasionally)
B. Average,
C. Above Avg (Use Upper RPM range quite often and accelerate hard)

4. VIN Number (last 6 digits) = 106438

5. Model (eg. Base, GT, etc) = GT

6. Automatic / 6 speed = 6 Sp

7. Octane (Number) of Fuel Used = 89

8. DSC/TCS = Yes

9. Miles to Date = 5600
10. Approximate % Time Driving with Windows Open = 10%

11. Approximate % Time Driving with AC on = 80%

12. State = CA
(I’ll later convert to Geographic Region)

MPG went up after 2000 miles, waiting to see if gets better after the oil change at 5000 miles.
Getting low 15 MPG now after 2000 miles.

Paul

canzoomer

This is really valuable stuff, especially for all the RX-8 owners now trying to make a case for compensation with Mazda.

I would gladly PAY for a copy of your analysis, with info on how to do the calculations you have done.

Thanks and keep up the GREAT work!

Sea Ray

I have a loaner while waiting for my car and have run only a few miles but I will report the basic info anyways. I drove 177 miles since yesterday, about 80 hwy at 75mph, the rest fairly aggressive in town.

1. 17.2 mpg
2. 50%
3. B-C (its a loaner
4. 103803
5. GT
6. 6 spd
7. 93
8. yes
9. 3200
10. 0
11. 0
12. Ky, temp in lower 40's

93rdcurrent

1. 14.1
2. 5%
3. B (it's winter)
4. 116546
5. GT
6. 6 spd
7. 92
8. yes
9. 1,588
10. 0
11. 0
12. Washington, Temps ranging between 20-41 f

LesPaul

1. 13.5 mpg
2. 10%
3. B.
4. 106064
5. Touring
6. 6 Speed
7. 91
8. Yes
9. 2,400
10. 0%
11. 0% (it's 20 degrees now!)
12. PA