Mazda 6 Forums banner

MPG

21K views 182 replies 95 participants last post by  Runningriot  
#1 ·
I've got to say that my fuel economy is bordering on atrocious. I have not calculated MPG yet, but I am barely getting more that 250 miles per tank. I realize that the tank is smaller than my 6s and the car has more horsepower, but even when I have driven like an old lady I cannot get much better. My low fuel light comes on at about 220 miles.

I am setting up an excel program to calculate MPG. I am having a brain fart though. How do I calculate accurate mileage. I note how many gallons I put into the tank, reset the trip odometer, and note my mileage the next time I fill up? then divide the number of miles by gallons? :headscrat:
 
#2 ·
24.7-25.2 MPG 350miles to tank. Majority of driving is 75 MPH freeway. But once off freeway, very deeeeep in the throttle, so I am pretty happy.
 
#5 ·
How do I calculate accurate mileage. I note how many gallons I put into the tank, reset the trip odometer, and note my mileage the next time I fill up? then divide the number of miles by gallons? :headscrat:
[/b]
Uh sort of, except you got the order of the steps wrong. You first reset your trip odometer when you refuel. (You must fill up until the pump automatically shuts off.) Don't make any calculations yet. Next time you refuel, do the math: note the trip distance, and divide that by your gallons filled. That will tell you what your average MPG was for the last xxx miles.

It helps to use the same pump at the same service station, since some pumps may shut off earlier or later than others and skew your results.

FWIW, the low fuel light comes on rather early. You still have about 3 gallons left when that light comes on. I have driven until the needle has moved past the "E" line and still only managed to put in 14.8 gallons. However, I did once run out of gas, and filled up 15.2 gallons. I suspect that the last .7 gallons left cannot actually be used due to the location of the fuel pump pickup inside the tank.

The most miles I've ever gotten from a single tank of gas is 376 (that was when the car died, fortunately on a city block close to a gas station). The best fuel economy I've gotten is 25mpg. When the car was very new, I was only getting 18-20mpg, but 6500 miles later with an 80% highway/20% city mix, I average about 22-23mpg.
 
#7 ·
I get about 350 miles per tank also. It takes about 16 gal to fill up, so that puts it at 22 mpg. My driving is about 80% highway averaging about 85 mph with frequent "passing" runs up to 110-115 mph. Around town it's lead foot all the way. I don't do alot of idleing or sitting in traffic so that may help.
 
#10 ·
I'm happy if I can stay above 18, which usually runs ~260-270 miles/tank when I fill. I drive almost exclusively city with a heavy foot. And I open it up when I get a chance at some open highway.
[/b]
Will the real backinblack please stand up ;)
 
#11 ·
i'm just turning 5k miles, i've noticed that my city mpg has increased to around 23-23.5, and hwy to 27-28. not too bad. that's a couple mpg better than a few months back.
 
#12 ·
I've actually kept it around at a surprising 25 in the city. That seems kinda high but my dad who drives it for now did the math and got that. I noticed the way he drives is him constantly being in a higher gear have the rpms 2 and under.
 
#13 ·
yeah you got it right divide total miles from odometer from number of gallons it took to fill the tank. if you reset it right after filling it up and divide by the decimal that should be accurate.
[/b]
Do the same thing but over a longer time period, say 3-5 tankfuls, if you can. This will average out the readings and eliminate any differences in the way the tank is topped up. Then you can use the Excel spreadsheet to get the most accurate economy figure over time.
1. As mentioned already, start off with trip odometer reset to 0 at the same time you refill the tank to full.
2. Next time you refill, again to full, record the # of gallons (full reading including all decimal points) and the trip odometer reading (full reading incl 10ths of a mile). Reset the trip odometer to zero again.
3. Repeat again for next refill. Record the #of gallons and trip odometer reading. Reset trip odometer.

You can refill at any time as long as you always record the gallons and odometer reading each time, and reset the odometer. You must always fill the tank to FULL, otherwise you will introduce errors in to the process. If a step is missed somewhere, just start from the beginning again - reset odometer, fill tank to full, record at next fill.

Enter each set of figures above into your spreadsheet as you get them, one column for gallons, one for trip odometer reading. Use the summation function to give the total for each column. Then select a blank cell somewhere on the spreadsheet and use the formula function to divide the trip odometer total by the gallon total, using their cell reference. This will give you a running fuel economy figure that's updated each time you refill the tank.
 
#15 ·
I have never gotten below 21.9 MPG. My highest was 26.5 MPG during a 80% freeway run. This is on 91 octane, and my car has around 3500 miles. At least 1 WOT run per trip (for fun). Approximately 18-20 trips a week. Fill up every 6-7 days at around 300-330 miles per tank, average 12.5-13.5 gallons per fill.
 
#16 ·
got 305 on my first tank of gas, probably 60-70% highway. Refilled with a little over 15 gallons. I am sure I topped it off more than the dealer did the first tank, so if I use my 15 gallon fill, it would come to 20.3 mpg....but it is probably more like 21 or so at least. I am sure it will get better as the break in miles accumulate. I hope so anyway, I still get 23-24 mpg in my GTO with 150 MORE whp.
 
#18 ·
Best ive gotten was 26 and worst was 19 used to be 1/2 city 1/2 HW...havent had a full fillup since my move to non highway driving to work
 
#19 ·
just took a 10 hour drive to tornoto. i got about 26 - pure highway driving - cruise control set at 72.
 
#20 ·
heres an exerpt from road & track about managing fuel consumption and getting the best mpg.

WOT/Short-Shifting

Remember Coach Grimbly's dictum about "driving with an egg under your foot"? Forget it. The most efficient way to reach cruising speed is wide-open-throttle (WOT) short-shifting. That is, not only do revs cost money, but so does prolonged motoring in lower gears, when throttling and pumping losses are their greatest.

WOT/short-shifting can save as much as 20 percent in city driving, worst to best case. In actual practice, rarely does traffic allow full WOT, but it's certainly fun — and efficient as well — to accelerate briskly through the lower gears to whatever the ambient speed happens to be.

Once there, the appropriate choice of gear is the one that offers modest rpm with relatively large (and constant!) throttle. Here, Coach Grimbly is vindicated. Dithering the accelerator is a pure waste of fuel, as is a slice-and-dice driving style. Read the traffic and go with the flow. Said one of my sources, "In fuel-economical mode, never request more power than is necessary to get to the next deceleration." There's a good enthusiast message here: Once up to speed, maintain it.

And, of course, avoid last-instant braking that wastes both fuel and brake hardware. A word on hybrid braking: It's useful to "shape the stop," that is, not to overwhelm the instantaneous capacity of regenerative braking. What's optimal is a relatively gentle initial pedal, followed by increased pressure as speed diminishes. Some hybrids have regen gauges that help in perfecting this technique.

Last, a lot of this is manual-shift-oriented, but thoughtful mimicking with an automatic can yield benefits as well.
[/b]
 
#21 ·
Okay, now I am thoroughly confused. One side of the fence says accelerate gently at low RPMs for best fuel economy. The other side of the fence says forget that and go WOT. I don't know who to believe anymore. Hard to test out too, since most of you know what happens when we go WOT in the Speed :burnout: :burnout:
 
#22 ·
heres an exerpt from road & track about managing fuel consumption and getting the best mpg.
[/b]
Can someone please translate this for me?
 
#23 ·
Can someone please translate this for me?
[/b]
into what? it's already in english. i can translate into chinglish if u want.

in simpler terms,

"here is an article from road and track magazine about getting better mileage"

or are u asking for a summary? in that case,

in city driving, it is better to open up the throttle than to feather the gas when accelerating. this can save up to 20% fuel consumption. the idea is to get to your desired speed quickly and maintain the speed with a gear choice at a reasonable rpm.
 
#24 ·
So, never mind how you get to cruising speed, once there is it better to be in the highest gear that doesn't bog, or is better to be up in the range where the turbo is working. For example, 50mph in 6th gear or 5th gear? Or 40 mph in 4th gear or 5th gear?
 
#25 ·
So, never mind how you get to cruising speed, once there is it better to be in the highest gear that doesn't bog, or is better to be up in the range where the turbo is working. For example, 50mph in 6th gear or 5th gear? Or 40 mph in 4th gear or 5th gear?
[/b]
the article says constant speed without dithering with a relatively large throttle. 50mph should be 5th gear. 40mph 4th gear. i might even try driving around 60mph in 5th gear. seems like the people who drive 75+ on this forum tend to get better mileage. i had a couple long trips in which i got 25mph on the highway at 65-70mph in 6th gear. thats the best ive ever gotten.