Checking Gasoline Mileage

fairly accurately. There are numerous ways of arriving at a guesstimate for mpg, but what have you found to be the most reliable method?

I have a mini-computer w/monitor feature on my car that gives various read-outs, it's interesting to see how gasoline usage is being registered under various driving conditions.

I usually just put the nozzle in the tank with the handle positioned in the fast

mode, and when it shuts off - remove the nozzle - and do the calculations necessary to come up with a mpg figure. not necessary totally accurate, but in the ball park.

different temperatures have an effect on volume, which affects the absolute usage.

mho vfe

Reply to
fiveiron
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Easy: fill the tank, drive the car, fill the tank again and divide the miles driven by the gallons put in. Do it enough times and then take the average.

To be most accurate, use a pressurized known volume container attached somewhere to the car and pipe it to the FI, then attach a seperate meter wheel to the back of the car to record milage. Run your car until it runs out of gas and compute the results.

Reply to
« Paul »

Fill the tank, let the nozz click off on its own. Note the mileage. Go through several fillups, just keep track of how much.

On the 'last' fillup, just let the noz clickoff on its own, and note the mileage.

The several fillups in the middle help keep the clickoff-error down.

Dave

Reply to
spamTHISbrp

The trip/milage computer in cars I've driven is pretty accurate and it compares favorably with the pencil and paper method. You will get the most accurate reading under either the high or low tech method by filling the tank and running it until almost empty.

If you are interested in an accurate statistic that can be used over time then consider a moving average in a spreadsheet. It will smooth out the minor differences that occur when the tank isn't quite filled up, etc, and make it easier to spot a trend.

Reply to
John S.

Statistics say try to get about 10 fillups in a row. What I do is compute milage for EACH of the ten. Then compute the standard deviation (do Google search for formula). That tells you the probable error in milage measurement.

Reply to
Don Stauffer

That's silly. Just take the entire distance and the entire fuel consumption for the gas mileage calculation. Why mess with standard deviations when a simple mean is all you need.

Reply to
AZ Nomad

Actually a moving average (mean) provides a statistic that isn't too ilfluenced by weekly blips and yet it does respond to trends. Average

5 fillups and store the average value. Next fillup drop the earliest observation, add the new one and store the average value.

It's easy to do in Excel and within a few months you have a pretty good idea what direction your mpg is headed.

Reply to
John S.

speaking of gasoline usage, there is, according to government statistics, 3-4 million

gallons of gasoline wasted daily - due to the under-inflated tires on moving vehicles.

that together with the 23 white house helicopters / air force one(s) -

it really runs the fuel usage - up.:--) Geeesh!!!! What a shame.

mho vfe

Reply to
fiveiron

And probably 300-400 billion gallons wasted daily due to traffic lights staggered so that no one ever pulls up to a green light. And probably billions more wasted by far-too-slow speed limits.

Reply to
clifto

Carefully record mileage and gallons purchased every time you buy gas. Enter data into spreadsheet.

I generally keep a running tally of a cumulative MPG & average MPG over the last 10 purchases.

Reply to
no_name

I've done the same. My standard deviation is less than 3%, so my individual tanks are fairly accurate. By tossing the high and low, my deviation dropped to less than 0.5%.

It makes it easy to tell when it's time for a tuneup. If my mileage drops by more than 1-2mpg, I need to start checking plugs,wires,tires,etc.

JW

Reply to
cyberzl1

but unless you drive the EXACT same route at the EXACT same speed under the EXACT same conditions you can (and will) have wildly fluctuating mileage.

I've put gas in my 01 Trans Am 143 times. Average is 19.12. Average over the last 10 was 18.23. Driving in rush hour traffic 5 days a week = a tank average around 17. Driving to the inlaws on country roads = a tank average around 28. Drag racing... well... equals about 6. :)

I don't worry about each tank being totally accurate - I'm looking for trends and an overall average. It's not a big deal if it's 20.1 mpg vs

20.25 mpg for your average Joe.

Ray

Reply to
news

What's your source for this claim? You originally asserted three BILLION gallons when you first mentioned it last month. Now you're down to three MILLION? I think you're making all of this up.

Current US population: 295,734,134 US gasoline use per capita (average): 464 gallons per year

295,734,134 x 464 = 137,220,638,176 gallons per year total US consumption.

Now, the allegation of 3,000,000 gallons wasted per day on underinflation:

3,000,000 x 365 = 1,095,000,000 wasted gallons per year.

That's 0.7%. Hardly a panic. Much more is probably wasted due to other things.

Oh, I suppose I should cite my sources:

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Reply to
Hugo Schmeisser

Because otherwise you do not know what the probable error is. By doing the standard deviation thing, you have an estimate of how accurate final average figure is. Otherwise, you have no idea whether your average reflects an uncertainty of 2 mpg or 0.2 mpg.

Reply to
Don Stauffer

That's why I coast and play the lights. I get through a lot of lights at

20-30 mph that folks beside me (or behind me who roar around me and race up to the light) have to start from a stop. Don't drive with your attention only thirty feet in front of the car- watch the lights ahead!
Reply to
Don Stauffer

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mho vfe

Reply to
fiveiron

That's way off topic...I thought you were looking for a reasonable way to track milage.

Reply to
John S.

Around here they've got it down to a science; to play the lights, you've either got to go a LOT under the limit or a LOT over.

20 or 65 in a 40 zone seems about right. And either way you're still forced to waste gasoline.
Reply to
clifto

one way to save gasoline while driving is to - move along at the lowest rpm that serves the purpose.

in some cases, if not all, while digging out - a release of pressure on the gas peddle will shift into a higher gear resulting in a lower rpm - consequently - saving a bit of gasoline.

with a tach reading as a guide - shifting "time" is made easier, once you get the hang of it.

mho v=83e

Reply to
fiveiron

moving through the lights without hesitation - is like running an obstacle course. damn if you do, and damn if you don't,

driving as near the speed limit as possible without lacing the traffic and making preparations to stop as soon as you are aware of an amber light - is often times a - good go.

that way you don't have to hurry up - to wait.:--)

leaving a car length of space between you and the car ahead while parked at a light - moves traffic more effectively.

putting only 10 dollars worth of gas, as needed, to maintain a half-full tank - should help to create a gasoline glut on the market - resulting in lower gasoline prices - has been advocated.

mho v=83e

Reply to
fiveiron

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