I saw this article a while ago and this has been a pet peeve of mine for a long time now:

https://www.vox.com/future-perfect/350382/gas-mileage-fuel-economy-mpg-gphm-gas-guzzlersBasically this is Vox's push for using "Gallons per 100 miles" instead of the traditional "MPG" that we are all familiar with. Gallons per mile is a MUCH more useful figure mathematically than MPG but GPM ends up being a tiny fraction and people seem to have trouble understanding those so they get around that issue by making it "Gallons per 100 Miles".

Obviously you can convert back-and-forth mathematically.

I just bought a Suburban. According to the EPA it gets 15/22 City/Highway. We also own a Honda Odyssey which gets 19/28.

Pop quiz, what saves more gas:

- Driving the Odyssey instead of the Suburban on a highway trip, or
- Driving a car that gets 38 MPG Highway instead of the Odyssey?

If you picked #2 you got tricked by the MPG issue. It seems like getting an extra 10 MPG is better than getting an extra 6 MPG so it *SEEMS* like getting 38 vs 28 is a bigger deal than getting 28 vs 22 but it isn't because you don't drive further. You are going to drive the same distance so the relevant figure you need is "GPM" or some derivative (like Gallons per 100 mi) not MPG.

For another example:

Lets say I am going on a trip with my wife, our four kids, our nephew, and his wife. That makes eight people. Suppose that we can all fit in the Suburban but NOT the Odyssey so our choices are:

- Take the Suburban, or
- Take the Odyssey AND a Toyota Prius that gets 57/56 City/Highway.

Mathematically, MPG's aren't useful. Here they are (highway since I said this was a trip):

- Option #1, the Suburban gets 22 MPG.
- Option #2, the Odyssey gets 28 MPG and the Prius gets 56 MPG.

So which is better? You can't tell from MPG's but you CAN tell from GPM, here are the Highway Gallons per Mile:

- Option #1, the Suburban uses 4.5 Gallons per 100 miles.
- Option #2, the Odyssey uses 3.5 Gallons per 100 miles and the Prius uses 1.8 Gallons per 100 miles for a combined total of 5.3 Gallons per 100 miles.

Taking the Suburban instead of the Odyssey AND the Prius would save us almost a gallon of gas per 100 miles.

The biggest problem, as the article explains, is that the focus on MPG's tends to lead to a focus on getting improvements that, in reality, are basically irrelevant. For example, if you could redesign that Prius to get 86 MPG Highway instead of 56 MPG Highway that sounds like a REALLY big deal but frankly, it isn't:

- Improving the Prius' MPG's from 56 to 86 saves 0.62 Gallons per 100 miles.
- Improving the Suburban's MPG's from 22 to 26 saves 0.70 Gallons per 100 miles.

For a while GMC offered a hybrid Suburban/Tahoe/Yukon/Escalade. At the time I thought that was a GREAT idea and the data says that it was but the consumers didn't care so they didn't sell and GM quit offering it.

Part of the problem, IMHO was that GM screwed up by putting a BIGGER engine in the Hybrid which minimized the gas savings. For 2013 they offered it in the Tahoe and in a 4x4 Tahoe there were two options for drivetrain:

- 6.0L Gas V8 Hybrid that got 20/23 and
- 5.3L Gas V8 that got 15/21

Even with the larger engine in the Hybrid, that still is a significant improvement especially around town but it doesn't look like a significant improvement until you convert to GPM:

- Hybrid used 5.0 Gallons per 100 miles City and 4.3 Gallons per 100 miles Highway.
- Non-hybrid used 6.7 Gallons per 100 miles City and 4.8 Gallons per 100 miles Highway.

IMHO, the smarter play would have been to offer the Hybrid with a SMALLER engine using the electric as a "helper" when needed. In that case the gap would have been much larger but it *STILL* would have "looked" minor when viewed in MPG's.