Tuesday, August 16, 2011

Hypermiling, Hypoconsuming.

Avoiding jack rabbit starts and coasting into stop signs can greatly improve the MPG your car gets.  These are among a long list of hypermiling techniques that, when carefully applied, have enabled attentive drivers to achieve MPG levels that greatly exceed their car's official MPG rating.

What sorts of levels can be achieved?

An Australian couple is driving across the US in an Eco Cruze with the goal of squeezing "2,000 miles from each fill-up of the car’s 12.6-gallon tank. That comes to 158.7 mpg and seems implausible, but if anyone can do it, the Taylors can."  

Or consider the performance of "Hypermiling king Wayne Gerdes and NASCAR driver Carl Edwards" who  "averaged 81.5 mpg during a three-day run that started Saturday and saw them double the 700-mile range Ford claims for the Fusion Hybrid."

Or, "Our hypermiling friends at Ecomodder.com took home three trophies at the Green Grand Prix, including top honors for an astonishing 99.7 mpg.  Darin Cosgrove, who founded the hypermiling site in November, 2007, tells us he used the “pulse and glide” technique “almost exclusively” to achieve that impressive figure during Saturday’s fifth annual event, which celebrates all things fuel-effient and alt-fueled. Four Ecomodders entered the event, held in Watkins Glen, NY."
Check out the large community of hypermilers at ecomodder.com, gassavers.org, and cleanmpg.com. (More on hypermiling at Mother Jones and Wired.  These articles also discuss the dangers of coasting, turning off engines at stoplights, etc.)
Let's look at these hypermiling numbers from a GPM perspective.  How much gas do these MPG improvements save?

First, let's translate hypermiling to a gas consumption metric.  Let's call extreme performance in saving gas "hypoconsuming."  Hypermiling and hypoconsuming are simply mathematical conversions of each other that depend on whether gallons of gas are put in the denominator (hypermiling) or numerator (hypoconsuming).

Here are some high (but achievable) levels of MPG and the amount of gas that is consumed over 100 and 1,000 miles:

Improving a car's MPG from 50 to 100 MPG saves 1 gallon over 100 miles.

Improving a car's MPG from 100 to 150 MPG saves .3 gallons over 100 miles. 

In contests to achieve the most impressive levels of MPG, hypermiling with highly efficient vehicles yields very large MPG improvements and very high levels of final MPG.  But, as hypermiling figures become more impressive, hypoconsuming figures become less impressive.  (The improvement from 200 to 250 MPG yields a 12 ounce reduction in gas use over 100 miles.)

Many SUV owners also try to hypermile.  They are often criticized by others for the inconsistency (hypocrisy?) of trying to save gas in an inefficient vehicle.  MPG invites the reaction, why bother trying to improve a 17 MPG to 24 MPG?  If we focused on hypoconsuming instead of hypermiling, however, we'd see the benefits of getting SUVs from 17 to 24 MPG.  The improvement saves over a gallon and half over 100 miles.

Would it ever be possible to hold a hypoconsuming contest where the winner would be chosen based on gas saved from the baseline (EPA) MPG?