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View Full Version : Great Explainer on Diminishing Returns of Fuel Efficiency



mp4guy
07-15-2014, 05:18 PM
Mentioned this before:

Fuel costs, which depend on vehicle fuel economy, miles driven, and fuel price, are an important factor in vehicle purchasing decisions. However, fuel economy improvement exhibits diminishing returns in fuel savings. For example, switching from a 10-mile-per-gallon (mpg) vehicle to a 15-mpg vehicle saves more fuel and results in greater fuel cost savings than switching from a 25-mpg vehicle to a 75-mpg vehicle. The fuel and cost savings of improving fuel economy from 12 mpg to 15 mpg are the same as increasing from 30 mpg to 60 mpg.

http://www.eia.gov/todayinenergy/detail.cfm?id=17071

ThingsAbove
07-15-2014, 09:40 PM
Good article.

In my case my Jeep Wrangler gets about 16mpg and my Abarth is averaging 33 on the same commute. My Jeep 35" tires on 17" rims cost $350 each while the Abarth tires are less than $100 each.

Fiat for the win!

On the other hand my Abarth won't be winching anyone out of a mud pit...

MikeThinks
07-15-2014, 10:14 PM
I've been trying to beat that into peoples heads for years. Paying ANY kind of premium to get a few MPG is insane. A year or two ago you could pay ~$2000 for the "economy" add ons for a few Fords, and it gave 2-3mpg more on a car that already got over 30, you should make good on that investment within a decade or two. Since most people these days dont drive 15 mpg vehicles, the same continues to apply even on a 35 mpg vehicle. You save more going from 22 to 32 than you do from 30-50

moosestang
07-25-2014, 08:10 PM
I get what they are saying, I do, but at the end of the day, a 75mpg vehicle is better than a 15mpg vehicle. I went from 16mpg to 30mpg, but if I could have went to a 80mpg vehicle instead, then I would have. there's no getting around the $2800 per year fuel cost vs. $700 per year, no matter how you spin it.

MikeThinks
07-25-2014, 08:34 PM
Its not a matter of saying that getting better MPG isnt good, its a matter of people getting caught up on a few MPG, which makes little real world difference once you get to 30MPG or so. Gaining 10 or 20 MPG is great, but because of the way our brains are wired we dont intuitively realize that as you get more efficient, it takes an increasingly larger increase in overall efficiency to make a noticeable improvement.

In your exceedingly unlikely example of going from 30mpg to 80mpg would only save you ~$1,000/year at $3.50/gal and 15k miles average....30 to 80 I mean WTH!

Lets say I told you I could retrofit your 45MPG average prius to get 15 more miles to the gallon for only $3000.00

If you drive 15k a year, at $3.50/gallon it would take you over 10 years just to break even. So you can see that even a big increase in fuel efficiency doesn't make economic sense in most cases.

lammie200
07-25-2014, 08:45 PM
...So you can see that even a big increase in fuel efficiency doesn't make economic sense in most cases.

For the individual in terms of expenditures, but this ignores things such as the environmental costs associated with increased fuel consumption. It is one side of a multifaceted issue. Specious.

Vaejovis carolinanus aka lowconabarth
07-25-2014, 09:51 PM
Miles per gallon is not as important to me as Smiles per gallon and my Abarth , Harley Davidson and my Outboard boat motor (when catching fish) give me high Smiles per gallon.

mp4guy
07-25-2014, 10:14 PM
I get what they are saying, I do, but at the end of the day, a 75mpg vehicle is better than a 15mpg vehicle. I went from 16mpg to 30mpg, but if I could have went to a 80mpg vehicle instead, then I would have. there's no getting around the $2800 per year fuel cost vs. $700 per year, no matter how you spin it.


Misses the point- if you look at the PERCENTAGES, that's all that really matters. Getting another 5 MPG on a car that used to get 15 MPG is important, and carries some weight. Getting a 35 MPG to get 40 MPG doesn't accomplish a lot. No vehicle I know of gets 80 MPG (unless you want to count Volts or BMW I series cars as getting that.) As an example you almost doubled your MPG by going from 16 to 30. There's no way you can duplicate that feat again because no IC car gets 60 MPG.

Even if development stopped dead in it's tracks, fuel consumption in America would STILL plummet at the replacement rate we're on now.

rustbucket
07-25-2014, 10:56 PM
Mileage, schmileage ... I went from having to add two quarts of oil per week (no leaks either) to none- I'm a happy man. :smile:

snakebite4767
08-02-2014, 08:54 AM
I bought a new Chevy 2014 Silvarado 3/4 ton HD Pickup. If I try hard, it gets 13.? mpg. After 3,000 mi, I could see that using this vehicle for my everyday travel was going to be a very expensive proposition. So... I bought a used (8,000 mi) 2013 Fiat 500 POP. I can get 40 mpg if I try, and 38.? if I just drive it and don't care..... this car is comfortable, fun to drive, and will totally pay for itself in 3 yrs. This is the best deal since I put all those solar panels on the roof.... they paid for themselves in 5 yrs, it's been Gravy ever since!

Snakebite

ophidia31
08-02-2014, 10:47 AM
Didnt read the article. But I look as a fuels savings vs buying a new car as well. The way I look at it is car car payments/repairs vs what your gaining in mileage vs the gas type used. Doesnt make sense to get rid of a car for another one that only gets a few mpgs more and tack on a car payment on top of it. Now if the mileage gain is large, say 10mpgs or more, then It may be worth it. Will you save money in the short? Maybe just a few dollars as the difference in price will still be negligable and you maybe even break even on it. But when the vehicle is paid off, then you will start to see the savings.

Mine for example I would use my Sky vs Abarth. (Still had car payments on both and used 93 in each) Trading the Sky that only had $11.5k left to pay vs the (after taxes etc) $20k I paid for the Abarth, my car payment went up $10 a month but I also gained 8mpgs. (Sky at 21 mixed vs the Abarth at 30 mixed) Usually do about $18-20 every week in the Abarth vs $25-30 every week in the Sky. So I pretty much just broke even. Once the Abarth is paid off, Ill see savings.