Is MPG the best way to measure fuel efficiency?

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Ben: Hey everybody, welcome to the podcast. My name is Ben Bowlin, and I write some videos here at

Scott: And I'm Scott Benjamin, the Auto Editor here at How you doing, Ben?

Ben: I am doing well, Scott, always well when we run into each other. How have you been?

Scott: Fantastic.

Ben: For our listeners, you guys just know our - I had a coffee situation, which Scott and our producer today, Tyler, just solved for me. If I don't have the ability to drink coffee, if our coffee machine is out or something, I should just get - What were you saying?

Scott: The chocolate-covered Espresso beans.

Ben: Will they give me that kick I need?

Scott: I think so, I think so. I'm not a coffee drinker.

Ben: I've always wondered why you're not.

Scott: No, soft drinks.

Ben: Yeah, soft drinks. That's cool, man.

Scott: Coke, Sodi, Pop, whatever, whatever you want to call it.

Ben: You go your own way.

Scott: Yeah, whatever region you're in, that covers it I think.

Ben: There are so many different names.

Scott: Yeah.

Ben: But we're not here to talk about that today. I just wanted to thank you on the air.

Scott: No, this is about fueling up though.

Ben: This is about fueling up.

Scott: See the link?

Ben: Oh, nice Scott.

Scott: Yeah, it worked.

Ben: Did you plan that one?

Scott: Not really.

Ben: That was pretty good though.

Scott: It sort of worked.

Ben: Okay, it worked.

Scott: What we're talking about though - I read something recently, and this is by no means new. This is old. It is probably a couple years old, but I kind of had this one on the back burner, and I thought we would talk about it, but we're just now getting around to it. There's an argument out there that says rather than the standard of what we use as miles per gallon (mpg) to measure fuel efficiency in a vehicle, that is maybe makes more sense to measure it in gallons per mile, now more specifically, gallons per 100 miles.

Ben: Now, a lot of people are not going to think that this is very different except for the 100-mile mark.

Scott: Yeah, well the 100-mile mark is just to make it a number that we can use really, so that it is large enough, I guess because when you're talking about gallons per 100 miles, you're talking about numbers that are like in 2, 3, 4, something real low like that. If you were to just say gallons per mile, the number would be a decimal point. That makes it just far more difficult, so we break it into gallons per 100 miles, or gallons per 1000 miles, and then gallons per 10,000 miles. You can do it anyway you want, but if you compare two vehicles in the same manner, you can get a much better picture of how much it cost you to drive your vehicle 100 miles, 1,000 miles or 10,000 miles - just in fuel cost, not operation cost.

Ben: So gallons per 100 miles is a measurement that a lot of people, at least here in the States, don't use. We use miles per gallon.

Scott: That's right, exactly, although in Europe they often use liters per 100 kilometers. That's a very standard measurement for them over there. So they get a better sense of - and they're not the only ones that use that, but they get a better sense of how much it cost them in fuel to go a certain distance.

Ben: See, that's something that I can use. You know what I'm about to talk about, right?

Scott: I think I do, yeah. Ben: Oh, gosh.Scott: Go ahead, bring it up. I want to hear it again.

Ben: I'm so lame, but I figured just in the interest of full disclosure. So my console on the dash of my beloved Monte Carlo is not all the way working. It's not completely dead, but the -

Scott: It's dead.

Ben: The gas gauge is not working. The speedometer works. The odometer appears to work, but the gas gauge has gone the way of the dodo, bought the farm, etc. As a result, it is of vital importance to me, to know exactly how many miles I can go on a gallon of fuel, or how many gallons it will take me to go 100 miles. So I just want you to know Scott, that this is of vital importance to me, and I am hanging, hanging on your every word.Scott: Okay, before we start, before we really get into this because it does get a little bit complicated. I'm gonna try to keep it real simple with using just round numbers, and make it easy on us. It's tough without having any kind of visual, to be able to tell people how this all works, but I'll tell you where to go to look up information, and hopefully you can follow along, or you can look this up later, and see just what I'm talking about because I'll use their examples, and maybe that will make it even more clear. The other thing is - We're not saying this should -

Ben: Replace -Scott: Totally replace or - Maybe in addition to is what maybe it should be.

Ben: A supplement.

Scott: Exactly. Maybe we should also have this number next to miles per gallon, and that might make sense. I don't think anybody is really saying that we need to completely replace miles per gallon. That's not the intent here. We're just letting you know that there's another way, another thought process out there, and it might make you think twice about another new car.

Ben: Oh, that's what we have to see because the results will be a little bit different if you calculate the difference between two cars miles per gallon versus between their GP100M, can I say that?

Scott: Yeah, I think that's the right way, yeah. You're right, this is really based on the idea that if you're looking to trade your vehicle. Let's say you've got a - Well, we will get into the examples, but for instance, let's say you got a car that gets 17 miles per gallon, and you want to trade it for a car that gets 23 miles per gallon. We can tell you how to figure out the fuel economy for that vehicle versus let's say, another vehicle that you might be considering to trade for, and see how much you're saving exactly, and you'll be surprised what we come up with here.

Ben: Yeah, I certainly was.

Scott: Yeah, it's not really as intuitive as you might think.

Ben: I would say it's counterintuitive, to be honest with you.

Scott: Yeah, that's right. Now, there are two guys at Duke University, and I'm looking through my notes here, hang on a second, I'll get it. It's Rick Lairick and Jack Soll. They Professors of Management, Associate and Assistant, and they were carpooling one day, talking about fuel economy on the way to work. They were in a Hybrid. They kind of said, well let's try to figure out some different scenarios where your economy is better or worse, and then try to average it out, try to figure out what's going on here exactly. They determined that miles per gallon can actually be a very deceptive measurement. It depends on your terrain. It depends on your climate. It depends on all kinds of different things. They said miles-per-gallon really depends on your style of driving. It depends on a lot of different factors. So they thought - Like I said, it's a deceptive measurement in their eyes. So they said, how can we work this to make it make more sense, make it even out between all of the vehicles, and start with a fresh slate. So they came up with this idea - Not that they came up with the idea, it's based on the liters per 100 kilometers idea. They've been working this through, getting funding from Duke to do some research - Or they did. I think it's over at this point. For example, they took a poll, and asked a lot of people, which would be the better vehicle to replace. If you had a 10-mile per gallon car, and you wanted to replace it with a car that gets 20 miles per gallon, so that's 10 to 20, or would you want to replace a 25 miles per gallon car with a car that gets 50 miles per gallon.

Ben: 50 miles per gallon?

Scott: Yeah, so you're replacing 10 with 20 or 25 with 50.

Ben: So you're doubling the miles per gallon.

Scott: In both vehicles, you're doubling the miles per gallon. So 10 to 20, 25 to 50.

Ben: Then I would of course - Can I answer?Scott: Yeah, of course.

Ben: I would, of course, want to go from 25 miles per gallon to 50 miles per gallon. Scott: That's what almost everybody who answered their survey question said. However, you'll find out that over a distance, and this isn't just - This is hard to explain without getting into it, so lets just get into it right now, okay?

Ben: Okay.Scott: You're better off trading the 10-mile per gallon car for a 20-mile per gallon car, and that does seem counterintuitive doesn't it? You want to say that you want 50 miles per gallon, that's the best scenario. Here's the way you look at it when you think about it in a distance of 100 miles. A 10-mile per gallon car uses 10 gallons of gas in 100 miles. So we're basing this all on 100 miles right now, okay?

Ben: Okay.Scott: So a car that gets 10-miles per gallon uses 10 gallons of gas. A car that gets 20-miles per gallon uses 5 gallons of gas to go the same distance.

Ben: So you're -Scott: 100 miles.

Ben: Oh, okay, I got it.Scott: Okay? A 25-mile per gallon car uses 4 gallons of gas for the same distance, whereas a 50-mile per gallon car uses 2 gallons of gas for the same distance, again 100 miles. So if you look at the gallons of fuel used, and I'll read them just straight down - 10, 5, 4, and 2. You have to compare the two, so you're talking about trading in a 10 mile per gallon car for a 20 mile per gallon car. The savings in fuel is really 5 gallons of fuel because instead of using 10 gallons, you're gonna use 5 gallons, so that's 5 gallons saved, right?

Ben: That makes sense.Scott: Okay, that, and we'll just say our fuel prices right now are $3.00 a gallon, right? That's $15.00, okay? So $15.00 is what it saves you every 100 miles.

Ben: Every hundred miles, okay.Scott: And you can extrapolate that out to 1,000, which would be $150, or even 10,000, which is $1500, so you can see the savings there. That's pretty big, right?

Ben: Yeah.Scott: Now, the car that you said was better to buy, the 25 versus 50, remember that's 4 gallons of gas versus 2 gallons of gas used in 100 miles so you are saving -

Ben: Two gallons.Scott: Two gallons per 100 miles.

Ben: Oh, that's so wrong.Scott: So, if you're saving 2 gallons per 100 miles, you are saving a total of $6 per 100 miles. So that means it is $60 for 1000 miles and $600 for 10,000 miles. So instead of saving $600 per 10,000 miles, wouldn't you much rather save $1500 per 10,000 miles.

Ben: You know me, Scott.Scott: I'm getting so trapped up in this. This is -

Ben: I think this is an excellent explanation because I'm also - you can see me scribbling along as well. Scott: I know it sounds terribly complex just hearing it, but it may be that, maybe it's simple for someone to follow along if you've got that kind of mind that can process that, but the thing is, if you look this up, or you figure it out on paper, the way I just described it, it's pretty clear how that set of numbers will give you a much more clear picture of how much you can save for a relatively short distance, 100 miles, or even a thousand miles. I go a thousand miles pretty quick in my car. It doesn't take that long, and when you talk about a year, you just determine how much you drive a year, and see the fuel savings between, a 10-mile per gallon car and 20-mild per gallon car, and so on. Isn't it odd that going from 10 to 20 is far more significant in savings for you than gong from 25 to 50?

Ben: It really is strange, and I guess it makes a little bit more sense when I think back on it because of the relationship with the numbers, you know, a lower mile per gallon is bad, and a higher miles per gallon is better. Scott: Well the smallest increase creates - and it's not that it creates a bigger increase, but a better savings, but a small increase in miles per gallon really does mean a big savings. I can give you one example of this - If you have a 15-mile per gallon car versus a 12-mile per gallon car. So you're talking about only a 3-mile per gallon difference. It's not significant really. It doesn't seem significant.

Ben: It shouldn't be.Scott: So let's take that one out to 10,000 miles, okay. Let's say you travel that in a year, it's a lease vehicle, you can only go 10,000 miles. So you're just talking fuel cost here okay. At 12-mile per gallon car versus a 15-mile per gallon car, you will save 167 gallons of fuel over that 10,000 miles by having a 15-mile per gallon car versus the 12-mile per gallon - just that 3-mile per gallon difference saves you 167 gallons in just 10,000 miles. Now I triple that amount because I go about 30,000 a year because I take road trips, etc. So 167 gallons x $3 per gallon is $501 that you save in one year just by having a car that gets 3 miles per gallon more, and if you take it out to 3 times that, which is what I drive, it's $1500 again.

Ben: Wow.Scott: So it's a significant savings. You don't think about it that way until you really see it laid out in gallons per mile. You just wouldn't think of that if you said, well 12 versus 15 miles per gallon, big deal, I'll go for the 12 because it's a splashier car, or whatever it is. Using your reptilian brain -

Ben: Oh, I knew - I wondered which one of us was gonna say that. Scott: Yeah, so if you recall back to the reptilian brain episode. So it's far more significant than you would think.

Ben: So do you think there is a possibility for car manufacturers and dealerships to pickup this way of looking at the numbers?Scott: Well, some reviewers have already started adding this to their reviews of vehicles online and in print ads, magazines, I should say. I think it's catching on, but not as fast as I think they wanted it to originally. I haven't seen it really in many places, but it's here and there. It's happening.

Ben: If there is a ground swell among the reviewers though, I think that definitely strengthens the possibility.

Scott: I think so. I mean it's been a couple of years since this has come out, since these professors at Duke came out with this idea, or broadcast that they've got this idea, and we should also include this number on the Monroney sticker on the window of every new car, but so far I just haven't seen it in many places, not many places.

Ben: Well, we still haven't really picked up the metric system in this country.Scott: No, no, no. I haven't told you exactly where you can find the stuff yet, but if you look on - You can find a little video that demonstrates this really well, and it will give you the 10, 20, 25, 50 demonstration I told you about -

Ben: That would be perfect. Scott: It's on You Tube. Just search the MPG Illusion - The MPG Illusion -

Ben: I like that title.Scott: It's real simple. It should walk you through exactly what I told you here, and maybe watch it once or twice like I did, and I finally got it. I understood what they were getting at, but it's an interesting little video clip. It's not very long, but I think if you dig into it you'll find it pretty interesting.

Ben: You know what else people should do while they're already on the internet?Scott: What's that?

Ben: They should check out the High Speed Stuff blog.Scott: Oh, good idea.

Ben: We don't really get to play too much, but it's got so many interesting things, and I think, well you know - Scott I know you can't say anything about it without being immodest. Scott: I'm blushing already.

Ben: He's blushing. It's crazy, I gotta stop. Scott: It is hot in here.

Ben: Yeah, who knows, but you're right though, it is. We're in a different studio today. Anyhow, so the blog is a great read. You can also find out more information about anything automotive related by checking this out at our website If you're looking for something that's not there, send us an E-mail, and maybe we can cover it.

Scott: Yup, and that is

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