Toyota’s new slogan may be “I want my MPG,” but some experts are arguing that MPG is a backwards way of measuring a vehicle’s fuel efficiency. Instead, they say, we need GPM.
We Americans are no strangers to weird measurements. In metric-friendly countries, water freezes at 0 and boils at 100. In America, there are twelve inches in a foot and 5280 feet in a mile; breakdowns that are a little tough to wrap your head around compared to the powers-of-ten-tastic metric system. Our MPGs are an equally confusing measure. Treehugger recently blogged that the relationship between the amount of gas consumed by a vehicle and its MPG rating isn’t linear … it’s curvilinear. I suck at math, but a quick look at this graph made the distinction fairly clear:
In other words, the gasoline savings of replacing a 15 MPG car with a 20 MPG car is about equal to the savings of switching from a 30 MPG car to a 60 MPG car. Here’s a quick breakdown of what gallons-per-mile looks like:
15 mpg = 660 gallons per 10,000 miles
20 mpg = 500 gallons per 10,000 miles
30 mpg = 330 gallons per 10,000 miles
45 mpg = 220 gallons per 10,000 miles
60 mpg = 160 gallons per 10,000 miles
Such a system may not make it immediately obvious how much a week’s worth of gas is going to cost you, but it makes vehicles’ relative fuel efficiencies much clearer. So despite the current focus on making small vehicles even more efficient (for instance, Honda coming out with an only-slightly-more-efficient hybrid version of the Civic), the biggest across-the-board gains will come from taking the least efficient vehicles off the roads. To wit: replacing the 2008 Ford Expedition, which gets just 12 MPG in the city, with something that gets just two miles per gallon more represents the same relative gas savings as replacing a 28 MPG car with a 40 MPG car. As Ecogeek points out, “this is why the Chevy Tahoe hybrid won green car of the year this year.”
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Wait, so are you saying I can trade in my Civic hybrid that gets 45 MPG, that I only have to fill up once every 3 weeks, but that has the pickup of Fred Flintstone’s jalopy for a Tahoe hybrid?! Hot dang!
posted by David K. Israel on 7-15-2008 at 11:11 am
I still like to know how much distance I’m putting into my gas tank. Here in Canada, we switched systems years ago, but now I think in terms of Kilometers-per-litre. Good is over 11, higher is better, lower means checkup needed.
posted by Art Waite on 7-15-2008 at 12:09 pm
We should be measuring MPGPP (miles per gallon per person). A minivan transporting 6 people is more efficient than a Prius with only a driver.
posted by William on 7-15-2008 at 2:43 pm
I agree with William – there was an article in our local paper about how, even though Hummers are fugly, annoying, and tend to be owned by douchebags, a Hummer with three people in it is a hell of a lot more efficient than 3 Civic Hybrids with one person each.
I drive a 2006 Jetta, and I get between 300 and 350 miles per tank of gas (depending on season). This is good to know since my gas gauge sticks and occasionally rises from 1/2 tank to 3/4 tank while I’m driving. [eyeroll]
posted by Rachel on 7-15-2008 at 3:47 pm
Yeah but a Civic is just as roomy inside as a Hummer. Have you ever ridden in one of those things?
posted by Antinous on 7-15-2008 at 10:52 pm
This isn’t the first time I’ve read this MPG vs. GPM stuff, and I don’t get it. One’s just an inverse of the other. Obviously going from 10MPG to 20MPG is a bigger improvement than 30 to 40. The first is doubling your efficiency. It’s the simplest of math.
What difference does it make in comparing two cars, whether you say they get 25 vs. 40 MPG, or use .040 vs. .025 GPM?
Sure replacing a 12 MPG SUV with a 14 MPG SUV may be as big of a savings as replacing a 28 MPG car with a 40MPG car, but it’s not as big a savings as replacing a 12 MPG SUV with a 40 MPG car (or even the 28 MPG car.)
posted by Patrick on 7-16-2008 at 1:02 am
Hmm..while it may be more efficient to put lots of people in an earth-killer like a Hummer or van, let’s not forget you can fit quite a few people in regular cars (Civics, toyotas) etc, and achieve even more efficiency.
Or even heaps and heaps of people in a bus!
Recaptcha: cheaper manage
(think it’s trying to tell us something…)
posted by Dawn on 7-19-2008 at 7:55 pm
While I have a hunch that the use of GPM (as a measure) will never catch on, dramatic improvements in mileage of the most thirsty vehicles are positively crucial.
Any “car of the year” award should be taken with more than a grain of salt. While the Tahoe Hybrid is great first effort on GM’s part, it still falls a good bit short of the 7-seat Highlander Hybrid when it comes to miles per passenger.
We will see massive improvements in MPGs as lithium battery technology is adopted. It’s happening right now in the after market. I wouldn’t be surprised to see a modded Highlander Hybrid hitting the 100 MPG mark in the near future. The Tahoe and Escalade Hybrids may follow, but only when enough units are produced.
The AFS Trinity Extreme Hybrid SUV (a tweaked Saturn Vue) is an indication of things to come. With a 40 mile all-electric range, it’s largely a question of packing enough plug-in battery (or in the case of AFS, ultracapacitor) power in-between the wheels.
posted by mpgomatic on 8-24-2008 at 9:22 am
It really irks me when I hear people or advertisers saying how far a car can go on “one tank” of gas. That’s got to be the stupidest way of measuring fuel efficiency ever thought up! Big whoop – so your VW can go almost 400 miles on one tank? My 1999 Chevy Suburban can go over 750 miles without a fill-up! Do you think that means I’m getting good fuel economy? No, that just means I have a 42 gallon tank. In reality, I get around 17 MPG on the freeway.
BTW, before you think I’m one of those douchebags who drives a big car just to be big, I have a 5-member family, and we also frequently drive a blind friend and her two kids around. So our 8 passenger vehicle is full.
posted by Also J on 4-11-2011 at 11:49 am
Also J:
My mini-van also seats 8 (which we often fill) and have a family of 5. It gets more than 50% better mileage than your suburban. The seats are more easily accessible by the passengers. It has more cargo space and is more versatile than yours. And, the safety and fatalities rates are better for mini-vans than SUV’s.
It has been my anecdotal experience that about 5% of SUV owners have a legitimate need for it. Once you blow all the chaff away, most people own those big vehicles for their ego.
posted by n2y2 on 4-11-2011 at 1:38 pm
I seriously doubt there exists a minivan with a larger cargo capacity than a suburban with all 8 seats installed. What van do you drive? What does it have behind the third row of seats, 4 or 5 square feet for cargo? A suburban has like 16 square feet (4′ by 4′), and that’s all behind the third row. Not to mention, a suburban can tow twice what any minivan can. That’s versatile.
posted by Carl T. on 4-11-2011 at 7:27 pm
I just know where I live, there is a direct correlation to the larger or more expensive the vehicle, the less the ability of the owner to drive it or center it in a parking space.
posted by Wayne on 4-12-2011 at 2:51 pm
According to the information specs given by intellichoice, my Sienna stacks up very well against the Suburban in passenger and cargo space. You must be under 12 or as limber as a gymnast to get into the 3rd row of a Suburban.
‘Also J’ mentioned nothing about towing, did he? Of the half-a-dozen people I know who drive a full-sized SUV full time because they need it to haul their boat, only one took it to the lake more than twice last year. Two didn’t move them out of the garage at all.
For that kind of frequency of use, it would be much more cost effective to rent a boat at the lake. Or drive a more sensible vehicle and rent the larger one for the odd weekend when it actually is needed.
That is what I mean by having a legitimate need. If people did the actual math rather than their assumptions, they might realize what a big waste the oversized vehicles are.
posted by n2y2 on 4-15-2011 at 4:00 pm