Fuel Economy, Testing It Correctly
 

People,
Its Amazing To Me How So Many Of Us Dont Understand How To Test Fuel Milage. Please Try This-
Warm Up -
Need To Be At Full Operation Temp, Warm Trans And Diff. Your Rotory Isnt Anyware Close To Efficiant Till Shes Hot, Cats Warm, Ect
Fill The Tank -
Find A Gas Station Near A Good Section Of Road That You Can Cruz Along 55 To 60 Mph. Fill The Tank, I Mean Fill The Tank All The Way! Use Premuim. Reset Your Trip Meter
Drive It-
Down The Road, 55 To 60mph For At Least A 35 Mile Run. Dont Stop, Stay Out Of Town.
Fill It Again-
Fill It, I Mean Fill It! Do It Know, Not Later. How Much Gas Did You Use!!!
Ill Bet Your Surprised!
Do The Math-
Dont Use The Fuel Gauge To Try To Figure Your Milage. Take The Miles On The Trip Meter And Divide By The Fuel You Added. No Fuel Gauge Is Accurate!!!! The Rx8 Has A Fuel Tank That Gives You Plenty
Of Resurve! Its Also Divided In Two.

Tips-
Stay Away From Higher Rpm !!! Secondary Port Opens At 3800rpm, Aux Port At 6200. Same With The Secondary And Aux Fuel Injectors.

Please Give This A Try, Post Your Results.


Good Luck!

We know you really meant to say for at least a 250 mile run - since a 35 mile run would only use around 1.5 gallons of gas, and then the normal error/variance on fillups would mean significant error on your mileage calculation. Right? ;)

Anyway - your method (warm at start of test, slow highway cruising) will generate a maximum MPG number, but won't represent typical real world mileage with cold starts and city driving mixed in. Sure, it's nice to know what the maximum MPG the car is capable of, but real world costs and real world mileage are what's important.

Regards,
Gordon

Care to share your results?

I don't use my fuel guage to measure my mpg. I use my trip meter, and the number of gallons that were needed to fill the tank. I perform this calculation every time I buy gas.

I tried different brands, and octane levels as well with no change...so I decided to use one gas station, one pump. I will wait for the pump if it is in use....

I am averaging 14.5mpg

I drive a mix of city and highway, probably 55/45 respectively. My mileage has dropped of significantly as cold weather has moved into my area. During the summer, I was getting about 200miles to 13.5 gallons. (14.5-8mpg) Now in the winter 180 miles to 13.5 gallons (13-13.3mpg).

I understand that the 8 has a saddlebag type fuek tank. As fuel transfers side to side, the fuel gauge will read differently. I tend to fuel up when the light comes on, and it is typically around 13.5 gallons.

Is this true? In the Mazda Owner's Book (or is it the little extra pamplet they give you) it says something along the lines of "don't warm up your car. As soon as the engine runs smoothly, drive" under the "how to get better mileage" section. I can't remember exactly where it is, but it's definitely in one of the things Mazda gave me. So I don't warm up the engine anymore. I just wait for the engine to settle then go.

When you are letting your car warm up in the driveway you are getting 0 mpg. I drive mine cold but keep the RPMs lower than 4K until it warms up. You won't be getting 16 mpg driving it while it's cold, but anything is better than 0.

I Agree!
Many People Want To Know There Average Milage. I Just Feel Some Of The Bad Press The 8 Gets Are Do To Not Fully Understanding How To Calculate Your Highway Milage. That Is The Most Accurate Way To Do It. I Personally Like To Test It With The Owner In The Car, On Short Trips (less Than 50 Miles).

Wow, miles divided by gallons, how'd you figure that out?

Will try again but. Last nite I drove from Parker az to long beach 270 mi. full tank on warm engine. used cruse control, 6th gear,3900 rpm 72 mph, no air. reached lb with 1\4 tank fuel
will fill up today ;but worst case is about 21-22 mpg

I DRIVE all city miles during the week, and get the usual about 16 mpg (trip usually says 200 when i fll up) but whenver I take my 8 on the highway for a road trip (more than 100miles) it gets SIGNIFICANTLY better mileage- i.e., the diff btwn highway and city miles seems to be more in this car than cars ive driven in the past- so don't be too discouraged by poor city 'everyday' miles. I took my 8 on a 200 mile trip this past weekend, and got nearly 300 miles on the 'tank', and when I divided gas by my trip when i filled up, rolled in at about 22 mpg, and i wasn't sticking to just 55-65, had defrost (aC) on, and was cruising about 85-90 most of the way.

The Value of Cruise Control
 

Haven't had a chance to check its effect specifically on the RX-8, but I learned long ago that using cruise control whenever possible has a significant effect on mileage in most cars. Constant speed cruising obviously increases mileage and cruise controls are generally more adept at maintaining a constant speed, avoiding even small variations, than one's right foot.

With this in mind, I switch to cruise control whenever possible in freeway driving and use the set/resume buttons in place of the foot pedal to control my speed. (Not going to enjoy the benefits of RX-8 handling/acceleration/braking on the freeway anyhow. I try to save the dinosaur juice for those opportunities to enjoy it.)

As I said, I haven't had a chance to check the effects on my new RX-8 yet since I'm still breaking in the engine and try to avoid long runs at a constant rpm, but in prevous cars I've noticed a difference of up to 20% in mileage when the cruise control is engaged.

Gas Tip
 

I am a noob to cars and stuff. I haven't complained about the mileage, but I realized I was measuring incorrectly. I assume most of you know this, but some people might have been making the mistake I made. I was doing my calculations based off of the tank size, but I realized I was actually getting better mileage when I use the amount of gas I actually used. On average I would have to put in 13 gallons everytime, but I was calculating with 15.9.

I just thought this might be useful for some other people. :cool:

Must have something to do with that new math they have been teaching for 20+ years :)

Good tip ... I think that most people don't realize when the orange empty light comes on that they still have a good amount of gas left. I believe that my light comes on when I have 10 liters left, so every fillup it's around 50L (getting me back to 60L).

I'm sure that most people would be pleasantly surprised to see their mileage shoot up! ha ha

#litres added / #KM travelled *100 = L/100Km :D
I've kept track since new.........makes average very accurate

Ya, I didn't notice that either. I'd just fill it up and look at the price, but I never really paid attention to the amount of gas I wsa putting in. All of a sudden it just dawned on me for some reason. :D

I'm not sure I know what to say... whew...

Really???

There are a\other threads that address this as well. I always use the gallons I pumped, and the miles on my trip meter. Otherwise, if you filled your tank from half, then you cant figure your mileage? I haven't gotten better than 15.5mpg in 14000miles with mixed highway/city driving.

nice idea jsh1120
i have thought about doing cruise control, but man, this car just makes me want to rev. i have been staying pretty low in rpms though. around 3k.

to spork or dark8
have your mileage improved from not letting the car warm up before drive? im interested in this information because ive been getting 13s and 14s even at my rpms.

thanks

I hate to be some forum asshole, but this guy makes it sound like he's explaining the Theory of Relativity or something, its simple math guy. :rolleyes: If someone cant calculate mpg, theyre retarded.

Gordon makes the best point, I dont care what the max MPG's are driving like my grandma.

Yeah, it's kind of funny. I wonder if he's done a search. There are so many far more technical threads on mileage.

It never occurred to me in all my years of driving that there was any other way to calculate mileage than by dividing the miles driven by the number of gallons used.

LOL - Actually, the metric guys divide the number of liters used by the number of kilometers driven. (The only other way I know.) By the way, the metric "l/100km" is different than MPG in that less is better.

you boob! duh.. of course you were getting an incorrect reading.. THE ONLY WAY to calculate gas mileage is miles driven by amount pumped... DUH! lol..... You should go back and get the g.e.d. It will be worth it! :)