OD has as well, but he has different gearing changes and FI that changes the whole game entirely.

I know there is discussion about running super lean for low load cruising. OD makes reference of it here: https://www.rx8club.com/series-i-engine-tuning-forum-63/bank-2-o2-sensor-affect-command-f-table-230104/ and notes that someone else is getting 28mpg running in the 15:1 AFR range, also FI though. Can't find the thread he referenced though.

 

Usually, spikes of good mpg are caused by underfilling on that single tank. What will happen then is your next tank will show below-average mpgs because you put in more than you started with. Sign up with fuelly.com and record over longer periods. Not many RX-8er's beat my mpg average over time.

Btw, better to be throttle off in gear than in neutral. In gear coast-down the fuel is completely shut off, neutral requires fuel to run.

 

My MPG is starting to go up with warmer temps having the last 2 tanks at about 19mpg. But, that’s only 2 tanks so not enough to be meaningful. Over winter I averaged 17.3-18.5. The 2 times on the track so far I’ve gotten between 7.8 and 8.2mpg with 3 full tanks.

 

This seems to make sense to me - but when I pulling the OBD2 data as I try this, the 6th gear coast down doesn't get nearly the mileage that a neutral coast does. By a factor of 3-5x, iirc.

Anybody else seen this? OBD2 fuel consumption data supporting neutral over "foot off pedal 6th gear coast"?

 

wow seeing all these high number is freaking crazy! I have a new engine bhr ignition new spark plugs new fuel pump and im still getting around 15-17 mpg :/ maybe an accessport will help..

 

ODB2 mileage data is theorized, not actual. The simple fact is that in neutral you are using a bit of fuel to keep the engine idling. If you are in gear with the revs higher than idle and do not have any throttle input, the ECU is not injecting any fuel at all. ODB2 mileage estimates are not really designed to account for this.

Low compression O2 sensor is failing, need transmission or diff fluid replaced, MAF sensor cleaned, etc... There is a laundry list of items that don't take much to kick you off the good mileage.

 

I have a ScanGauge 2 from my old car that I tried on my RX8 for a while but I yanked it out of the car cause I was tired of seeing my crap gas mileage. I never measured a full tank of gas cause I do a lot of short distance driving but I did look to see what I was getting as I drove. I know it's not 100% accurate but it gives you a pretty good idea.

City Driving: 12-15 mpg

Highway Driving: 17-25 mpg

Short Distance Driving: 5-8 mpg (not a fully warmed car/ couple mile driving)

There have been a few unique times on the highway where I would hit around 30 mpg at a speed of about 70 mph but it wouldn't stay there for long. I also noticed I got better gas mileage around town when I shifted at about 3500-4000 RPM. Kinda wierd but you gotta take those ScanGauge's with a grain of salt.

 

OBD2 data is calculated through a formula using MAF, AFR and VSS .... like RIWWP said, all theoretical.

 

series 2 transmission would help a lot too

 

It's the math: .1 mile / 0 gallons = ?? Any system doing "instantaneous" mpg calculations has to handle divide-by-zeros as an exception. What the programmers decide to show varies. Manufacturer, in car displays tend to be optimistic (duh). The Scangauge allows calibration of their unit to match the car being measured, but few bother to go through the trouble.

 

 

I have a Scangauge, which is accurately calibrated, confirmed by manual calculations. During the week my regular 25 mile commute is very consistent, so I know what is normal for my car, conditions, and driving style. On a bad day (cold weather, driving too fast) I get 21-22 mpg. On a good day (warm weather, staying under 70 mph) I get 27-28 mpg. And, everything in-between, depending...

Yesterday was a "good day" !

 

This one time at band camp.

 

Those are good numbers! But, in a real world, this doesn't cut it for 99% of us...lol

 

Post counts don't mean anything to 99% of us either.

 

I don't know what you mean (not that it matters to me).

My driving is not in some imagined controlled environment. It is real world commuting: 8 miles city, 20 miles freeway, one-way. Ocean Blvd / 2nd St / 405 fwy / Sand Canyon Ave. Usually 1 redline before entering the freeway, when conditions allow.

 

I wouldn't worry too much about what others think about getting 29 mpg in your 8. If you are sure you did all the calculations correctly then you have done something many would like to achieve. They don't believe it because they don't want to.

 

You probably looked at the wrong trip meter...