What's your fuel economy to weight ratio?

[SVOboy]

What's the theory behind your equation bunger?

[Silveredwings]

Miles per gallon is meaningful. it's a ratio that has an inherent explanation: it's the average number of miles you can go with each gallon of fuel.

Miles per hour is how many miles you are going on average each hour.

What does mpg/lb really indicate? It's because mpg is generally inversely proportional to weight. The lighter the car, the higher the mpg, so of course the number will get bigger if you divide a smaller weight into the higher mpg number.

The reason it doesn't make much sense to me is because I haven't seen a practical explanation. For example, if you take mpg/ton and use it as some kind of standard, are we saying that's how many mpg a car can get for each pound? Does that scale? If I take a 2000 lb car that gets 40 mpg, I get 40mpg/1 ton = 40. Then if that car's weight were increased to 4000 lb, would I get 80 mpg? No, of course not.

You can either compare your efficiency to a standard like EPA (such as it is), or compare two numbers that are normally proportional in comparison. In other words, multiply numbers that are inversely proportional, or divide numbers that are proportional. This makes for a comparative index that shows real gains in the world of vehicle utility.

Then there's power-to-weight. The higher the power and lower the weight, higher the number. It's meaningless except for raw acceleration numbers.

Please, continue to elaborate. I'd like to hear more.

[zpiloto]

I'm so confused now that I'll just follow the thread and see where it goes.. I'm still trying to figure out why the weight needs to be in there to compare cars. If your car is heavy or powerfull won't the EPA number reflect the car abilities with low numbers? What ever is decided it needs to be simple enough for us hard heads to do.

[thisisntjared]

weight * mpg
= weight * distance / energy

do you understand the significance now?

weight / distance / energy
doesnt make any sense.

yes its not a precise statistic and many other things can factor in, HOWEVER isnt the same true with the power/weight ratio? other factors being traction, suspension and gearing?

i dont like the points system, too complex and superfluous.

i still stand behind weight*mpg.

here is a quick notepad table of the people who have posted so far.
3880 * 45.0 / 1000 = 174.600 escape hybrid (Escape_Hybrid)
2070 * 66.8 / 1000 = 138.276 honda civic (basjoos)
2392 * 55.4 / 1000 = 132.517 (diamondlarry)
2200 * 56.5 / 1000 = 124.300 honda delsol (krousdb)
1800 * 59.3 / 1000 = 108.519 for the Blackfly (MetroMPG)
2950 * 34.4 / 1000 = 101.480 (zpiloto)
2500 * 39.8 / 1000 = 99.500 (Randy)
2965 * 29.9 / 1000 = 88.653 nissan altima (Compaq888)
2130 * 40.2 / 1000 = 85.626 honda civic (thisisntjared)
2000 * 40.0 / 1000 = 80.000 honda crx (SVOboy)
1807 * 43.0 / 1000 = 77.701 metro (95metro)
2350 * 32.2 / 1000 = 75.670 (kickflipjr)

maybe the number should be divided by 2000 so we have ton*mile/gallon

3880 * 45.0 / 2000 = 87.300 escape hybrid (Escape_Hybrid)
2070 * 66.8 / 1000 = 69.138 honda civic (basjoos)
2392 * 55.4 / 2000 = 66.254(diamondlarry)
2200 * 56.5 / 2000 = 62.150 honda delsol (krousdb)
1800 * 59.3 / 2000 = 54.260 for the Blackfly (MetroMPG)
2950 * 34.4 / 2000 = 50.740 (zpiloto)
2500 * 39.8 / 2000 = 49.250 (Randy)
2965 * 29.9 / 2000 = 44.327 nissan altima (Compaq888)
2130 * 40.2 / 2000 = 42.813 honda civic (thisisntjared)
2000 * 40.0 / 2000 = 40.000 honda crx (SVOboy)
1807 * 43.0 / 2000 = 38.851 metro (95metro)
2350 * 32.2 / 2000 = 37.835 (kickflipjr)

[Escape_Hybrid]

Originally Posted by JanGeo

Congratulations!

Now how many MPG per lb does that come out to . . .

This is an interesting concept, and one that I think would help compare apples to oranges ( or a Ford Escape Hybrid to a Prius ).

Based on weight, I beat the socks off any other hybrid.

My FEH weighs 3880 pounds with a full tank of gas.
(I have a certified truck scale at work.)

My best segment over flat terrain was 75.5 MPG for 11.9 miles.
The round-trip home that night was 68.3 MPG for 20.2 miles.

So...75.5 / 3880 = 0.01945 MPG per pound. Does that make sense?
No... don't think so... having a heavier car makes the number smaller....
Gotta multiply, I think....

75.5 x 3880 = 292940 MPG Pounds.

I think MPG Pounds is the correct route to go. Agree?

Now take an Insight. *estimate, I've never owned one

*109 MPG x *1900 pounds = 207100 MPG Pounds.

Wooo hooo! Going by that, I can beat an Insight in my Ford SUV?

Does everyone agree this is a fair way to compare? Thanks.
-J

[Escape_Hybrid]

Originally Posted by MetroMPG

FYI, my 3 month (3 tank) average is currently 59.3 (US). The car weighs 1830 lbs.

Edit: instead of the original suggestion of mpg/weight we're going with this formula...

vehicle weight (lbs) * MPG / 1000

... to get "pound miles per gallon (/1000)"

1800# * 59.3 / 1000 = 108.519 for the Blackfly

What's yours?

My FEH weighs 3880 pounds with a full tank of gas.
(I have a certified truck scale at work.)

My best segment over flat terrain was 75.5 MPG for 11.9 miles.
My second best was 68.3 MPG for 20.2 miles.
My tanks average about 45 MPG.

75.5 x 3880 /1000 = 292.240 ( best case )
45 x 3880 /1000 = 174.600 ( average )

-John
P.S. I think this is a pretty good quick and easy comparison. And yes, it does statistically make sense.
Now, if you want to throw in air drag, go ahead. That will boost my numbers, as this is a small SUV shaped like a brick!

[GasSavers_Randy]

Originally Posted by thisisntjared

2500 * 29.8 / 1000 = 74.500 (Randy)

That's 39.8 thankyouverymuch.

The reason this sort of number is interesting is when comparing very different vehicles. Like a semi... 70k+ lbs, but they get 6 or so mpg on the highway. That would easily trounce the best so far. Things like trains or ships burn insane amounts of fuel... unless you factor in weight, then they trounce anything on the road.

Note that the new CAFE standards are based on this sort of concept. It measures 'footprint'... the area of wheel base times wheel track, then reduces required MPG based on it. Critics say manufacturers will push bigger vehicles, but proponents say small vehicles kill and therefore shouldn't be pushed by CAFE. No, seriously, that's what they say... check out highwaysafety.org.

[thisisntjared]

crap sorry man i fixed it.

regarding the CAFE standars, some people are just too busy pushing their own agenda to care about truth.

[SVOboy]

You never added me, nice man. 80 is my rating, 40 mpg. Figure out the rest!

[Escape_Hybrid]

Originally Posted by Randy

That's 39.8 thankyouverymuch.

The reason this sort of number is interesting is when comparing very different vehicles. Like a semi... 70k+ lbs, but they get 6 or so mpg on the highway. That would easily trounce the best so far. Things like trains or ships burn insane amounts of fuel... unless you factor in weight, then they trounce anything on the road.

YES! Exactly! This is a measure of efficiency! A train is very efficient on fuel! Which is what most people want to know... how efficient their car is.
This is a measure of "usefulness" also. An Insight or Geo uses fewer absolute gallons of gas than mine, but those cars are also less useful. ( in the sense of hauling goods, going on vacation, comfort, etc. )