What's Your Car's Gas Milage? Poll

[Cyrus]

No, there is nothing "strange" about it, and it is linear.

You can plot the miles you will get as a function of the number of gallons of fuel. It is a system based on the number of GALLONS not miles, because we purchase GALLONS of gasoline.

Where are you getting this 'inverse' relationship from?

This is middle school math...

y=mx+b

y-miles
m- MPG
x-#gallons in your tank
b= 0 (no gas, no miles)

You are making such a simple concept wayyyyyyyyyyyy too complex my friend.

The fact is, no one cares about how many gallons to the thousand miles.

 

[Rach3]

What I mean is

\mbox{gallons of fuel } \propto \frac{1}{mpg}

for a trip of definite length, and vice-versa.

 

[Cyrus]

But I told you ten times now, no one cares, because no one pays by the mile man!

 

[blue636]

When I had my Kawasaki EX500, I got about 57-60mpg. On my Suzuki SV650S I get about 44. On the Kawasaki ZX6R 636, I'd get about 36-38 mpg.

 

[Rach3]

Cyrus:

Perhaps I am blind, but I really have no idea what you mean by that. People who buy hybrids don't suddenly start driving three times more often; people who buy SUVs don't drive three times fewer. Trip lengths are not a function of fuel efficiency, they are function of how far apart destinations A and B are and what roads are in between them. So a consumer will driver more or less X miles a month, regardless of what they're driving in. We can treat that length as a constant, because it is independent of the mpg rating.

Now, as far as my meager brain can fathom, the economically interesting number here is how many dollars the consumer is spending on fuel. Since the trip lengths are constant, this rate of spending goes as to

\mbox{spending } \propto \mbox{gallons of fuel } \propto \frac{\mbox{distance traveled }}{\mbox{ fuel efficiency (miles per gallon)}}

And as long as our consumer isn't drastically changing his driving habits, the distances involved are constants:

\mbox{spending } \propto \frac{1}{\mbox{ fuel efficiency \bf{(miles per gallon)}}}

Hence fuel efficiency goes inversely as to our economically interesting quantity, the $.

Now, if we were to use a more sensible fuel efficiency, gallons of fuel per distance, the above equations become

\mbox{spending } \propto \mbox{distance traveled } \times \mbox{ fuel efficiency \bf{(gallons per mile)}}

Which is nicely linear in fuel efficiency.

 

[Cyrus]

I give up, I am going to go drive my car into a wall sticking my head out the window

 

[Rach3]

I give up, I am going to go drive my car into a wall sticking my head out the window

And you made this decision without thinking about said car's fuel efficiency! That supports my point!

 

[Rach3]

Actually I suppose it would be called "fuel inefficiency", but I still think it's the more interesting number.

 

[Cyrus]

Ok, replace wall with you. I am going to drive into you (with a hummer that has a leaky gas tank)!

Look, my car has a 13 gallon tank. It's going to cost me 13*(going price of gasoline) each time I fill it. THATS what I care about.

I know that each time I fill my tank, it will cost me that much money, and I can go that far on that full tank of gas.

Why on Earth would I want to start calculating my average trip length, multiply that by 1000, divide that by MPG!?

 

[Rach3]

Look, my car has a 13 gallon tank. It's going to cost me 13*(going price of gasoline) each time I fill it. THATS what I care about.

But that's just the point! How often will you be filling it?!

 

[Cyrus]

Easy,


My tank holds 13.56 Gallons. It gets 21MPG, so every 284.76 miles.

If I drive let's say 1000 miles a month, ~4 times a month. Wow, was that so hard?!

NOPE!

 

[Rach3]

Well, DUH.

 

[ShawnD]

Using US gallons..

92 Ford Tempo
1.8L I think (I'll check that)
4 cylinders
4 gears
city mileage: ~25
highway mileage: ~33

My job is about 70km away from where I live, so I still get raped at the pump.


I find this rather strange

I ride the bus It costs me $12 a month

Here in Edmonton, Canada the bus cost $58 per month.

 

[ShawnD]

Well then, let's simplify it and go with our Canuk way. Litres per 100 kilometres.

It's actually a myth that Canada uses this system. If you go to a Honda or Nissan dealership, you will see little stickers in the windows of cars that say things like "25mpg city, 28mpg highway". Canada still uses mpg because km and L cannot be compared to anything. If the American EPA has a bunch of gas mileage estimates in mpg, and you see something that says L/100km, how can you even compare the two? One is reciprocal and the units for both distance and volume are different. It's extremely hard to compare them unless you happen to have a calculator handy and know the appropriate conversions. You don't even need to know what a mile or a gallon is, you just need to know that 30mpg is better than 25mpg.

 

[wolram]

Why are you all talking as if mpg is a fixed amount, is it best case, average case, worst case, driver dependent? or just a hypothetical number.

 

[Moonbear]

Why are you all talking as if mpg is a fixed amount, is it best case, average case, worst case, driver dependent? or just a hypothetical number.

It's usually the one time you remembered to check the odometer when filling up twice in a row. It's going to seem lower if you're doing a lot of stopping and starting, driving only short distances, etc., and higher on a long road trip when you can keep a nice steady speed on the open highway. Run the air conditioner, and you lose more mileage. So, the sticker in the window when you buy the car is usually the best possible under perfect conditions. Actual mpg is usually a bit lower due to the way real people drive.

 

[wolram]

It's usually the one time you remembered to check the odometer when filling up twice in a row. It's going to seem lower if you're doing a lot of stopping and starting, driving only short distances, etc., and higher on a long road trip when you can keep a nice steady speed on the open highway. Run the air conditioner, and you lose more mileage. So, the sticker in the window when you buy the car is usually the best possible under perfect conditions. Actual mpg is usually a bit lower due to the way real people drive.

For sure MoonB, as i hate the tax man so much i practice ecconomy driving,
easy on the gas, look ahead keep moving if possible, coast down hills (bad practice i know) but what the hey if there is no hill to go up afterwards and you do not bleed off to much speed, auto boxes are the killer you yanks should ban them, they sap so much power.

 

[Astronuc]

I think we should be using gpm instead of mpg. The savings in going from 8 mpg to 12 mpg, is much greater than in going from 28 mpg to 32 mpg, even though the "difference" is the same, 4 mpg. The more logical system is clearly linear in fuel. I mean, who here, when driving, thinks to theirself "well, I've decided to use 2.37 gallons on this trip, so where will I go?" Rather, we think "I'm going to X today, so how many gallons will I use?" Who agrees?

8mpg = 0.125 gpm
10mpg = 0.100 gpm
20mpg = 0.050 gpm
30mpg = 0.034 gpm
60mpg = 0.017 gpm

Tanks (military) measure mileage in gpm - and probably Humvees, too.

I believe race cars (Formula 1) also measure gpm. In both cases it is a concern about range.

I think mpg is a reasonable measure of efficiency for most driving. On the highway, I use distance and mpg to figure range and when to stop for gas.

Comparatively, when considering purchasing a car, I would tend go with the higher mpg car.

Also, fuel efficiency depends on the type of driving (e.g. speed, terrain, city vs highway, load in the car, and even wind resistance (from experience driving in W. Texas where wind made a huge difference in mileage)).

PS - I just filled up my Odyssey and realized an average of 23.7 mpg - with half of that driving on the highway.

 

[Hootenanny]

For sure MoonB, as i hate the tax man so much i practice ecconomy driving,
easy on the gas, look ahead keep moving if possible, coast down hills (bad practice i know) but what the hey if there is no hill to go up afterwards and you do not bleed off to much speed, auto boxes are the killer you yanks should ban them, they sap so much power.

The taxes in this this country, especially those for petrol are criminal! Seriously, Gordan Brown should carry a 'swag bag' rather than his red briefcase!

 

[DaveC426913]

Chrysler 300M. 260 miles on a 12.5gal tank = ~19MPG.

If I were looking to save money, I'd have bought a different car...

 

[wolram]

I would run my car on used chip shop oil, but knowing the bloody fuzz in the UK they would be chasing me for a free meal.

 

[Moonbear]

Tanks (military) measure mileage in gpm - and probably Humvees, too.

Yeah, if you need to measure it in gallons per mile, you really should think a bit harder about fuel economy.

 

[Jimmy Snyder]

I drive a Honda Civid Hybrid. I drive 55 mph on the highway. I've been getting 45 mpg.

 

[ShawnD]

Actual mpg is usually a bit lower due to the way real people drive.

If you don't drive like a jackass, the EPA estimates are actually very accurate. My Tempo is 14 years old and the gas mileage is still pretty close to the EPA estimates. It only differs from the estimates when driving on snow or gravel.

 

[Ivan Seeking]

After just checking on a long run, I was happy to find that our largest car - the gas hog - is getting just over 30mpg with the A/C running and with the Oregon/California mountain passes in the middle. The other car gets about 35 Hwy and about all we drive is hwy speeds. Hoping to get a diesel hybrid and burn locally produced biodiesel next.

btw, giving out the make, model, and year of your car, is a bad idea if you wish to protect your anonymity.

 

[Cyrus]

What? Knowing my car won't get you my bank account numbers.

 

[wolram]

The taxes in this this country, especially those for petrol are criminal! Seriously, Gordan Brown should carry a 'swag bag' rather than his red briefcase!

I so agree, soon the government will be sending out knights to torture us
out of our money and build splendid castles out of their ill gotten gains,
but the time will come when the land is empty.

 

[Ivan Seeking]

What? Knowing my car won't get you my bank account numbers.

Well, normally one wouldn't need to worry about it, but if someone was trying to get information for credit fraud or whatever, information like this is useful. It could help complete the map to your name, address, etc. It's probably a good idea to avoid revealing any definitive identifying information about yourself.

 

[Cyrus]

This information is public knowledge. All they need is your name.

It's really quite useless, they need something better than that.

For instance, my bank account number is 5659-3330-582...

Edit: Oh crap......

 

[Ivan Seeking]

I'm just tellling you what I've heard and read from the alleged experts.

They also warn against telling tales of college party life or other compromising information. Some companies are now searching for this information in order to make hiring decisions.