This is a guest article by Wallace Thomas, an NMA member.

Miles per gallon seems like it’s easy enough to understand, but it’s not. Let give you a hypothetical situation:

Let’s say that my wife and I have two vehicles, the first, is one of those high performance 4wd SUVs that goes like stink, can tow my trailers, but the way we use it, it’s averaging 10 MPG per year of use. The second is a pretty cool sports car. It’s real fun to drive, handles well, and the way we use it, it’s averaging 25 MPG per year of use.

Now, just to make my point, we’ll say that both cost about the same. Both are driven the same amount of miles per year — we’ll say 15,000, and both are the same year — 2005. Now, we realized that replacing two cars at the same time gets quite expensive, so since they both are now 4 years old, we’ve decided we’ll replace one now, the other in 4 more years. This way, we can cycle through, getting one new vehicle every 4 years, keeping each for 8 years and 120,000 miles.

So now we’re looking at two vehicles to decide which to replace.

The proposed replacement for the SUV is an extended cab pick-up. We still need the ability to tow (what with the waverunners, the Harley — there a joke hidden here — and the camping trailer), still need passenger room, but are considering a little more utility, and a little less sport.

The pick-up we’re looking at, with the way we use it, would average 12.5 MPG for a year of use. That’s a whole 2.5 MPG improvement. Woo-hoo.

The sports car replacement would be a sports coupe. Seating for 4, still fun to drive, and the way we use it, it would return around 33.3 MPG for a year of use. That’s an 8.3 MPG improvement — over an already decent MPG. Pretty good, huh?

So, which one will save us more money in fuel?

Well, with a 2.5 MPH improvement versus an 8.3 MPG improvement, it pretty obvious. So the SUV goes, and in comes the pick-up with it’s 12.5 MPG. Huh? What about the 5.8 MPG better we would do with the Coupe? That’s the big problem.

In Europe, they use a different rating system. It’s Liters used per 100 Kilometers. What if we converted to Gallons used per 100 miles? We could call it GPHM (Gallons Per Hundred Miles!)

So here’s the story. The old SUV at 10 MPG is using 10 GPHM. The new pickup, at 12.5 MPG is using 8 GPHM, an improvement of two gallons for every 100 miles driven. In 15,000 miles of use per year, that’s 300 gallons not purchased.

The old sports car used 25 MPG. That’s 4 GPHM. The new one, at 33.33 MPG is using 3 GPHM. an improvement of one gallon for every 100 miles driven. In 15,000 miles of use per year, that 150 gallons not purchased. An improvement of 8.3 MPG saved one half the money and fuel that the improvement of only 2.5 MPG did!

But people don’t think that way. They see the bigger MPG improvement and assume they’ll save more money.

To get the same fuel savings as the truck, the sports car would have to be replaced with a car that gets 50 MPG throughout the year! How many sporty coupes are there around that do that? Now consider this: If you already were getting 33.33 MPG, you would need to get 100 MPG to get the same fuel saving!

So, what I’m putting out there for your mull around is that we should SERIOUSLY look at how we measure and compare fuel use.

I’m including a very simple chart to compare MPG to GPHM. Look and see, if you were to change from a 10 MPG vehicle to a 20 MPG vehicle, you would save more fuel – and money (5 GPHM savings) than switching from a 20 MPG vehicle to a 100 MPG vehicle (4 GPHM savings)! As I said in the beginning, we’re being suckered by miles per gallon ratings.

10 mpg = 10 GPHM

11.11 mpg = 9 GPHM

12.5 mpg = 8 GPHM

14.28 mpg = 7 GPHM

16.66 mpg = 6 GPHM

20 mpg = 5 GPHM

25 mpg = 4 GPHM

33.33 mpg = 3 GPHM

50 mpg = 2 GPHM

100 MPG = 1 GPHM