Gas mileage

[Engineer]

Originally posted by: nakedfrog

Originally posted by: Turin39789
where does my bicycle fit into the equation?

Well, as you get 0 gallons per mile (or 0 miles per gallon, if you prefer) any vehicle is a huge improvement as far as gas mileage goes.

It's actually infinite (or undefined) miles per gallon as it would be ZERO gallons...

miles / ZERO = undefined (infinity as gallons approaches zero)...

 

[AkumaX]

Originally posted by: Engineer

Originally posted by: nakedfrog

Originally posted by: Turin39789
where does my bicycle fit into the equation?

Well, as you get 0 gallons per mile (or 0 miles per gallon, if you prefer) any vehicle is a huge improvement as far as gas mileage goes.

It's actually infinite (or undefined) miles per gallon as it would be ZERO gallons...

miles / ZERO = undefined (infinity as gallons approaches zero)...

chuck norris can define it.


*runs*

 

[DrPizza]

Originally posted by: Baloo
Yeah, there's an article on CNN from the Associated Press about this very topic here I'm sure this is where you got the idea for your post; You ripped the entire article without a word of credit to the writer.

Apparently you've never heard of National Public Radio - you know, the source which I credited in the first post? That wasn't good enough for you? In fact, *I* credited the original source, although not the author of that source. I think there's a fair argument to be made that CNN ripped their entire story from NPR.

However, it's not really news - it's something that's pretty simple common knowledge to many of us - something that I go over in my pre-calculus class & have gone over for years when I do a unit on statistics. (I especially point out how increasing your mph from 50 to 60 saves more time than 60 to 70.) I merely thought that I'd point it out since gas seems to be a common topic these days. I certainly don't credit either news organization for anything other than pointing out that people don't understand mpg as much as they think they do, and for the idea of illustrating this point with numbers. Then again, using numbers to illustrate the point really shouldn't be credited either as it's the most likely way to demonstrate this topic.

Oh, and one thing that happened before the NPR story - New York State had a question on the freshman regents exam: calculate the mpg for 2 cars. Nearly all students got that part correct. The next part: "which car is better?" I'd estimate that nearly 33% of the students thought 12.5mpg was better than 15mpg because it was "less gas." If you asked me the day before the exam how students across the state would do on that problem, I never in a million years would have expected that. Upon reflection though, how many 14 year olds really have that much exposure to mpg to have a good grasp on the concept?

 

[fbrdphreak]

Um, yeah. This would be why the British measure fuel economy in amt of fuel over a given distance.

1L / 100km
2L / 100km
3L / 100km

And so on. Linear, simple, easy - even for the stupid masses. Some have been suggesting such a change here, but I think the change would break the collective public's one remaining brain cell.

 

[ShawnD1]

Originally posted by: AkumaX

Originally posted by: Engineer
miles / ZERO = undefined (infinity as gallons approaches zero)...

chuck norris can define it.

Quoted for ban.

Um, yeah. This would be why the British measure fuel economy in amt of fuel over a given distance.

1L / 100km
2L / 100km
3L / 100km

I always thought this was a stupid unit because it's unfamiliar to most people in Canada, and we end up using the mpg number right next to it (new car stickers show both).
Sticking with our current mpg system seems a lot easier, even though I don't even buy gas in gallons. Old car gets 24mpg, monthly gas is $200, new car is 38mpg, new cost is (200/38)*24 = $126. Very easy.

 

[soulcougher73]

I am having a hard time wrapping my head around this for some reason and i work in an engineering field LOL.

It just seems weird that going from 15 to 21 MPG which is only 6 more MPG would save more gas then going from 27 to 51 MPG which is 24 more MPG.

What type of vehicle it is shouldnt matter in this comparison either. Just pretend they are all the same vehicle but get different MPG.

 

[Engineer]

Originally posted by: soulcougher73
I am having a hard time wrapping my head around this for some reason and i work in an engineering field LOL.

It just seems weird that going from 15 to 21 MPG which is only 6 more MPG would save more gas then going from 27 to 51 MPG which is 24 more MPG.

What type of vehicle it is shouldnt matter in this comparison either. Just pretend they are all the same vehicle but get different MPG.

If you are using a large quantity of gas, it only takes a small percentage improvement to save many gallons. It takes a much larger percentage to make smaller "useage" vehicles save the same or more gallons.

Example: Car getting 1 mile per gallon would use 12,000 gallons per year (based on DrPizza's OP). Going from 1 mile to 2 miles would save 6,000 gallons per year. Sure, the 51 mpg car will save more OVERALL but the OP is talking of the difference in gallons used per year, not overall gallon useage per year.

 

[Gibson486]

Originally posted by: hanoverphist

Originally posted by: Gibson486

Originally posted by: Engineer
Going from a 15mpg SUV to a 51mpg hybrid saves 564.7 gallons too. Sure, going from one to class up to another might not be as much as going from 45 to 51, but remember, they are still getting above 45 and you're now getting 21. Unless somebody comes up with something quick, we're still running out of the stuff at some point (the algae that shits crude oil looks nice though! ).

It makes sense to save as much as you can as long as you're purchasing a vehicle anyway. It does not make sense to rush out and buy a car (usually) just to save gas.

Once again, the engineer exposes the mathamatician's flaw

it wasnt a flaw, it was stated that the truck was needed for whatever reason, and would continue to be a truck regardless of the outcome. so, in that case, going to a truck that gets 21mpg was the better choice. of course replacing a 15mpg truck with a 51mpg hybrid car would be the optimum, but not necessarily the realistic outcome.

that's the point. It was a joke, anyways, about how mathamaticians look too much into numbers while engineers generally look at the bigger picture.....

Atleast Engineer got the joke, so that is all that matters

 

[Gibson486]

Originally posted by: Engineer

Originally posted by: DrPizza

Originally posted by: Engineer
Well, you are indeed correct....but you still "use" 3,900% more. Maybe gallons per mile does make more sense than miles per gallon.

Originally posted by: TheTony
..., in terms of pure savings, gallons per mile is a more accurate measurement than miles per gallon.

You two are geniuses!

LOL. The one forgotten item in this equation is that if everyone went from 30 mpg to 12,000 mpg, gas would fall to $0.50 per gallon instead of the $4.00+ per gallon and you would save far more! (j/k but true to some extent).

Originally posted by: rasczak
You guys broke my brain

You need to sit in on an Engineering managers meeting on new equipment for a short while...your brain would really be broke then!

I miss those meetings....

where the head engineer starts talking and everything he said just makes your brain take a dump.

;sigh;....I hate my job

 

[Engineer]

Originally posted by: Gibson486
;sigh;....I hate my job

Maybe this little post is just what I needed. Deciding on whether to interview for another job or not....maybe I really "love" my job more than I think and sometimes, the status quo might not be so bad, eh?

Thanks for the insight...but sorry you hate your job.

 

[Gibson486]

Originally posted by: Engineer

Originally posted by: Gibson486
;sigh;....I hate my job

Maybe this little post is just what I needed. Deciding on whether to interview for another job or not....maybe I really "love" my job more than I think and sometimes, the status quo might not be so bad, eh?

Thanks for the insight...but sorry you hate your job.

nah man, I'd do anythign to go back into real engineering. Consulting stinks. It's just "engineers" that really want to do business but also want to have the engineering title in their name because it makes them feel special.

Boss - "You made a really good design"

Me- "Ummm....I did not design anything, I just put the stuff together"

Boss - "great job!"

Me - ;sigh;.....off to do more autocad

 

[2Xtreme21]

While I don't disagree with the OP, I want to show the large flaw in basing decisions on purely percentage:

If my hourly earnings increased from $10 to $18, I got an 80% raise.

If my hourly earnings increased from $1000 to $1500, I only got a 50% raise.

If you look at it in purely percentage terms, the $10 -> $18 person got a better deal than the $1000 -> $1500. What people neglect is an equal frame of reference.

 

[Gibson486]

Originally posted by: 2Xtreme21
While I don't disagree with the OP, I want to show the large flaw in basing decisions on purely percentage:

If my hourly earnings increased from $10 to $18, I got an 80% raise.

If my hourly earnings increased from $1000 to $1500, I only got a 50% raise.

If you look at it in purely percentage terms, the $10 -> $18 person got a better deal than the $1000 -> $1500. What people fail to neglect is an equal frame of reference.

Welcome to the world of marketing. There are no engineers or mathematicians (usually), just people who know that one number is bigger than another.

 

[dullard]

This is just a classical point-of-diminishing-returns problem.

Suppose you were stranded alone on an island with no food, but plenty of water. Suppose you could get 1 burger a day. You'd be thrilled. Now, say you can get two burgers a day. You'd be even more thrilled (but you won't gain quite as much as you did going from starvation to one burger). Each of those burgers makes a major impact on you and your life. Now say you go from having 10 burgers to 11 burgers a day. Or even from 30 to 12000 burgers a day. You know what? You just don't gain much at all from these additional burgers (maybe you could turn the buns into a shelter, but other than that you gain little). The benefit of going higher and higher just means lower and lower returns for each additional item.

Same goes for MPG. Or just about anything else in the world.

Except beautiful women, you can never have enough of them.

 

[KillerCharlie]

It's pretty simple math... there's been an article about this on the major news websites the past few days.

 

[Perknose]

Years ago, but in my lifetime, full size American pickups were significantly smaller and lighter than a "mid-size" Dodge Durango. They had six cylinder engines. Almost NO ONE had fucking 4 wheel drive. Everyone managed just fucking fine.

My Dad was an engineer kicked up to management. He drove rwd Buicks. Here in the Northeast, he NEVER got stuck, even in the fiercest of winter storms. He carried chains, and used them when he absolutely had to. On now laughable bias ply tires, he got through the snow without ever getting stuck, even once, because HE DAMN WELL KNEW HOW TO DRIVE IN THOSE CONDITIONS, and, no muss, no fuss, he taught me how to do the same.

Face it. Today, we're self-indulgent pigs. Most of us, even for work, have MORE vehicle than we really need.

Collectively, we suck. And I include myself in this grim assesment, should you be asking. :|

 

[Foxery]

Originally posted by: ShawnD1
Old car gets 24mpg, monthly gas is $200, new car is 38mpg, new cost is (200/38)*24 = $126. Very easy.

Originally posted by: KillerCharlie
It's pretty simple math... there's been an article about this on the major news websites the past few days.

Never overestimate the intelligence of the average person. Most Americans won't finish reading / listening to any sentence which includes more than two numbers next to each other, never mind ones with funny symbols inbetween.

Originally posted by: Perknose
Face it. Today, we're self-indulgent pigs. Most of us, even for work, have MORE vehicle than we really need.

Collectively, we suck. And I include myself in this grim assesment, should you be asking. :|

I have multiple vehicles myself, and while I can justify why each one of them serves a distinct purpose in my life, I occasionally realize that owning multiple vehicles, generally speaking, makes me a @#$%.


Much thanks for DrPizza for the informative breakdown. I sent your post to a few non-AT readers as well, as my parents have a similar situation to that described in the OP.

 

[DrPizza]

Originally posted by: 2Xtreme21
While I don't disagree with the OP, I want to show the large flaw in basing decisions on purely percentage:

If my hourly earnings increased from $10 to $18, I got an 80% raise.

If my hourly earnings increased from $1000 to $1500, I only got a 50% raise.

If you look at it in purely percentage terms, the $10 -> $18 person got a better deal than the $1000 -> $1500. What people neglect is an equal frame of reference.

You're actually agreeing with me then: the majority of the public thinks they know enough math to get by, but they don't realize how often they make bad decisions or get screwed. Years ago, I worked at a non-profit organization. The majority of the workers thought that it was way too top-heavy with management & that many of them were overpaid for what they actually did (close to nothing; honestly.)

One year, the CEO announced that everyone would get the same pay raise: 3%. Most of the employees were quite satisfied to know that everyone was going to get the same amount more. However, as it took a long time for them to work out the details, the pay raise was retroactive 3 or 4 months. Unlike many organizations, people often shared with each other details that they probably shouldn't have. A lot of the people couldn't figure out why the manager's retroactive checks were more than their own, since everyone "got the same raise."

 

[PricklyPete]

I preach this to people ALL the time. It's a percentage game.

 

[dmcowen674]

Originally posted by: DrPizza
I heard something similar to this on NPR the other day, and thought it was worth repeating here. Ultimately, I find that the problem relates to people going with their intuition, rather than their desire to do the math (and often, a lack of mathematical ability.) And, unfortunately, "uninformed" public opinion sometimes drives political policy making, which often overlooks more important sides of issues.

This concerns gas mileage: (I remembered this in a furnace efficiency thread where 80% may be cheaper in the long run than 95% efficient)

Suppose a married couple has two vehicles; and each is driven about the same number of miles each year - 12,000 miles. The husband drives (and requires) a truck; and his only gets about 15mpg. The wife has a nice smaller car that gets about 27mpg. The couple decides that they can afford payments on one new vehicle, thus they'll be able to replace only one of the two that they currently own. The choices are to replace the 15mpg truck with a 21mpg truck, or to replace the 27mpg car with a 39mpg car. And, they realize that for just a little bit more money, they might even be able to swing the payments on a 51mpg hybrid, rather than a 39mpg car. What should they do?

Well, most people's intuitions would tell them, "get the hybrid you idiots, that's 23mpg more!" And, while some of you might have done the math in your heads, I'm sure that some of you realize that the hybrid people are wrong, else I wouldn't have written this thread. Thank you for your trust.

Ask this question of most people though, and they'd think it was a no-brainer. You only gain 6mpg with the truck, compared to gaining 12mpg for the car. Or, gaining 23mpg for the hybrid, almost doubling the current mpg!!!

The math: For 12,000 miles, the amount of gas each uses in a year:
15mpg: 800 gallons
21mpg: 571.4 gallons
27mpg: 444.4 gallons
33mpg: (I know, this wasn't an option) 363.6 gallons
39mpg: 307.7 gallons.
45mpg: 266.7 gallons
51mpg: 235.3 gallons

Notice: there isn't a linear relationship between the mpg you gain, and the gallons you save. Going from 15mpg to 21mpg saves 228.6 gallons (This is what upgrading the truck gets you.) Going from 21 to 27 (which wasn't an option) saves only 127 gallons. Going from 27 to 33 saves even less: 76.4 gallons, and 33 to 39 saves only 55.9 gallons. From 39 to 45: 40 gallons, and from 45 to 51: 31.4 gallons.

So, switching from a 15mpg truck to a 21 mpg truck makes much more sense (saves 228.6 gallons) than going from 27mpg to 39mpg (saves 136.7 gallons) And, it still makes more sense than even switching from the 27mpg car to the 51mpg hybrid (which would save 209.1 gallons)

Also worth noting: The difference between a 51mpg hybrid, and a magical 100mpg dream vehicle would "only" save 115.3 gallons of gas a year. That's less gas savings than going from 21mpg to 27mpg. Going from that magical 100mpg vehicle to the absolutely insane 12,000mpg vehicle would save 119 gallons of gas. And, that's even less than the savings in going from 21mpg to 27mpg.

For those of you who drive trucks, large vans, SUV's, etc., (many not because they have a choice of what type of vehicle they own) realize how much of an effect 2 or 3 mpg due to better maintenance can have on your mileage. As a nation, we'd probably save more gas by encouraging the owners of "gas guzzlers" to maintain their vehicles better, than by mandating some arbitrary increase in required average gas mileage by the manufacturers.

Big Oil pay you for that disertation?

We should not be using ICE period.

 

[wetcat007]

Did people seriously not realize this?

 

[Eeezee]

The correct answer is to get a job that doesn't require a truck. There are very few professions that require you to own a truck. It was always those people who needed to own a truck or SUV that were the most adamant supporters of said vehicles; what they never realized was that by trying to make SUVs trendy, they were only really hurting themselves (ie higher gas consumption = higher demand = higher prices = everyone loses)

It has always seemed obvious that one should replace the less efficient vehicle, assuming it gets used just as often.

 

[ICRS]

Originally posted by: dmcowen674

Originally posted by: DrPizza
I heard something similar to this on NPR the other day, and thought it was worth repeating here. Ultimately, I find that the problem relates to people going with their intuition, rather than their desire to do the math (and often, a lack of mathematical ability.) And, unfortunately, "uninformed" public opinion sometimes drives political policy making, which often overlooks more important sides of issues.

This concerns gas mileage: (I remembered this in a furnace efficiency thread where 80% may be cheaper in the long run than 95% efficient)

Suppose a married couple has two vehicles; and each is driven about the same number of miles each year - 12,000 miles. The husband drives (and requires) a truck; and his only gets about 15mpg. The wife has a nice smaller car that gets about 27mpg. The couple decides that they can afford payments on one new vehicle, thus they'll be able to replace only one of the two that they currently own. The choices are to replace the 15mpg truck with a 21mpg truck, or to replace the 27mpg car with a 39mpg car. And, they realize that for just a little bit more money, they might even be able to swing the payments on a 51mpg hybrid, rather than a 39mpg car. What should they do?

Well, most people's intuitions would tell them, "get the hybrid you idiots, that's 23mpg more!" And, while some of you might have done the math in your heads, I'm sure that some of you realize that the hybrid people are wrong, else I wouldn't have written this thread. Thank you for your trust.

Ask this question of most people though, and they'd think it was a no-brainer. You only gain 6mpg with the truck, compared to gaining 12mpg for the car. Or, gaining 23mpg for the hybrid, almost doubling the current mpg!!!

The math: For 12,000 miles, the amount of gas each uses in a year:
15mpg: 800 gallons
21mpg: 571.4 gallons
27mpg: 444.4 gallons
33mpg: (I know, this wasn't an option) 363.6 gallons
39mpg: 307.7 gallons.
45mpg: 266.7 gallons
51mpg: 235.3 gallons

Notice: there isn't a linear relationship between the mpg you gain, and the gallons you save. Going from 15mpg to 21mpg saves 228.6 gallons (This is what upgrading the truck gets you.) Going from 21 to 27 (which wasn't an option) saves only 127 gallons. Going from 27 to 33 saves even less: 76.4 gallons, and 33 to 39 saves only 55.9 gallons. From 39 to 45: 40 gallons, and from 45 to 51: 31.4 gallons.

So, switching from a 15mpg truck to a 21 mpg truck makes much more sense (saves 228.6 gallons) than going from 27mpg to 39mpg (saves 136.7 gallons) And, it still makes more sense than even switching from the 27mpg car to the 51mpg hybrid (which would save 209.1 gallons)

Also worth noting: The difference between a 51mpg hybrid, and a magical 100mpg dream vehicle would "only" save 115.3 gallons of gas a year. That's less gas savings than going from 21mpg to 27mpg. Going from that magical 100mpg vehicle to the absolutely insane 12,000mpg vehicle would save 119 gallons of gas. And, that's even less than the savings in going from 21mpg to 27mpg.

For those of you who drive trucks, large vans, SUV's, etc., (many not because they have a choice of what type of vehicle they own) realize how much of an effect 2 or 3 mpg due to better maintenance can have on your mileage. As a nation, we'd probably save more gas by encouraging the owners of "gas guzzlers" to maintain their vehicles better, than by mandating some arbitrary increase in required average gas mileage by the manufacturers.

Big Oil pay you for that disertation?

We should not be using ICE period.

Then what should we use. Their is nothing practicle on the market now that doesn't use a ICE.

 

[JEDI]

Originally posted by: DrPizza
I heard something similar to this on NPR the other day, and thought it was worth repeating here. Ultimately, I find that the problem relates to people going with their intuition, rather than their desire to do the math (and often, a lack of mathematical ability.) And, unfortunately, "uninformed" public opinion sometimes drives political policy making, which often overlooks more important sides of issues.

This concerns gas mileage: (I remembered this in a furnace efficiency thread where 80% may be cheaper in the long run than 95% efficient)

Suppose a married couple has two vehicles; and each is driven about the same number of miles each year - 12,000 miles. The husband drives (and requires) a truck; and his only gets about 15mpg. The wife has a nice smaller car that gets about 27mpg. The couple decides that they can afford payments on one new vehicle, thus they'll be able to replace only one of the two that they currently own. The choices are to replace the 15mpg truck with a 21mpg truck, or to replace the 27mpg car with a 39mpg car. And, they realize that for just a little bit more money, they might even be able to swing the payments on a 51mpg hybrid, rather than a 39mpg car. What should they do?

Well, most people's intuitions would tell them, "get the hybrid you idiots, that's 23mpg more!" And, while some of you might have done the math in your heads, I'm sure that some of you realize that the hybrid people are wrong, else I wouldn't have written this thread. Thank you for your trust.

Ask this question of most people though, and they'd think it was a no-brainer. You only gain 6mpg with the truck, compared to gaining 12mpg for the car. Or, gaining 23mpg for the hybrid, almost doubling the current mpg!!!

The math: For 12,000 miles, the amount of gas each uses in a year:
15mpg: 800 gallons
21mpg: 571.4 gallons
27mpg: 444.4 gallons
33mpg: (I know, this wasn't an option) 363.6 gallons
39mpg: 307.7 gallons.
45mpg: 266.7 gallons
51mpg: 235.3 gallons

Notice: there isn't a linear relationship between the mpg you gain, and the gallons you save. Going from 15mpg to 21mpg saves 228.6 gallons (This is what upgrading the truck gets you.) Going from 21 to 27 (which wasn't an option) saves only 127 gallons. Going from 27 to 33 saves even less: 76.4 gallons, and 33 to 39 saves only 55.9 gallons. From 39 to 45: 40 gallons, and from 45 to 51: 31.4 gallons.

So, switching from a 15mpg truck to a 21 mpg truck makes much more sense (saves 228.6 gallons) than going from 27mpg to 39mpg (saves 136.7 gallons) And, it still makes more sense than even switching from the 27mpg car to the 51mpg hybrid (which would save 209.1 gallons)

Also worth noting: The difference between a 51mpg hybrid, and a magical 100mpg dream vehicle would "only" save 115.3 gallons of gas a year. That's less gas savings than going from 21mpg to 27mpg. Going from that magical 100mpg vehicle to the absolutely insane 12,000mpg vehicle would save 119 gallons of gas. And, that's even less than the savings in going from 21mpg to 27mpg.

For those of you who drive trucks, large vans, SUV's, etc., (many not because they have a choice of what type of vehicle they own) realize how much of an effect 2 or 3 mpg due to better maintenance can have on your mileage. As a nation, we'd probably save more gas by encouraging the owners of "gas guzzlers" to maintain their vehicles better, than by mandating some arbitrary increase in required average gas mileage by the manufacturers.

thank you for the analysis.

never realized that. :Q

always thought of cost analysis of new car price vs cost of driving old car and where the breakeven point is. (Lexus SUV hybrid breakeven is in DECADES :Q you only gain 1mpg w/it's hybrid.)

 

[PlasmaBomb]

Originally posted by: nakedfrog

Originally posted by: DrPizza

Originally posted by: Engineer

Originally posted by: DrPizza
that going from 15mpg to 30mpg saves more gas than going 30mpg to 12,000 mpg.
(29.9625mpg is the even point, if my math is correct.)

Whoa, you're got your math wrong there!!!

Really? 12,000miles divided by 15mpg = 800 gallons per year
12,000 miles divided by 30mpg = 400 gallons per year.

That saves 400 gallons per year.

12,000 miles divided by 12,000mpg = 1 gallon per year (obviously) - a savings of only 399 more gallons. So, the 15 to 30mpg jump saves more gas than a 30 to 12,000mpg jump would.

Maybe someone should plug this stuff into an Excel sheet

Hehe way ahead of you...

A Picture is worth a thousand words...