The Volt’s 230 MPG: Are Miles Per Gallon Still Relevant?


The Volts 230 MPG: Are Miles Per Gallon Still Relevant?

Chevy Volt’s 230 MPG sounds good, but what about 60 MPK or 25 KPM?
The array of advanced car technologies hitting the consumer marketplace has brought about enough boasts, confusion, and questions to fill a gas-guzzling SUV’s cargo hold.

GM’s CEO Fritz Henderson announced this week that the company’s much anticipated Chevy Volt is the undisputed winner in the miles per gallon race, claiming under new EPA guidelines the Volt will hit 230 miles per gallon , the first car to ever earn triple digit recognition. Not to be outdone, Nissan fired back a few days later to its Twitter-base of fans that its just-announced, all-electric Nissan Leaf would be rated at 367 MPG, also using Department of Energy guidelines.

By comparison, Toyota’s fuel-sipping Prius hybrid looks like an outright gas hog at 51 MPG and the Honda Insight hybrid appears ready for the “cash for clunkers” program at 41 MPG. Ditto for the Ford Fusion hybrid and Toyota’s Camry Hybrid .

But what about MPK and KPM comparisons And what about MPGGE and GHGP It’s the new language in your car future.

The EPA’s methodology behind the Volt’s eye-popping 230 MPG rating, and other so-called extended range electric vehicles , is still under wraps — though GM and others claim to be using it — and the agency says it can’t comment since it has not yet tested the Volt. In the meantime, the Society of Auto Engineers continues to tinker with its new hybrid test protocols. It has a lot of automotive fans scratching their heads about the recent Volt MPG claims and how pure electric vehicles or hydrogen fuel cell vehicles stack up.

The EPA’s National Vehicle and Fuel Emissions Laboratory in Ann Arbor, Mich., says it’s revising its formulas to reflect more real-world representations of “driving cycles,” that is, up hills, down hills, acceleration rates, city miles, and highway miles — the driving conditions that affect fuel efficiency, or in the case of hybrids or electric cars, how long the battery will last. This is why the EPA says “it cannot confirm” GM’s mileage claims, but is happy they are innovating such fuel efficient cars.

With the Volt, GM is among the first to make some marketing hay from the unreleased EPA revisions, which evidently take into account on-board gasoline generators like the Volt’s. Specifically, GM bases its 230 MPG boast on a blend of the Volt’s electric-only mode — which has a 40 mile range limit — and charge-sustaining mode, with its 1.4 L electric generator running.

Here’s the breakdown: The 230 MPG number, according to GM’s Frank Weber, global vehicle line executive for the Volt, is a measurement of the car’s “city driving cycle” — that’s the 40 miles it can go without gas, plus one daily electric charge-up, plus a little extra help from the gasoline it might need to continue to charge its batteries when they get low while driving in the city. It’s basically measuring the Volt’s electric-only-mode mileage capacity. If the Volt got out on the highway — where it’s powered largely by gasoline — and traveled 200 miles the MPG would drop like a stone, and likely be more in line with other hybrids.

In the end, the EPA’s new EREV testing process, like the one the California’s Air Resources Board uses, may not actually measure gasoline usage at all, but kilowatt hours per 100 miles or KP/100M. They’d then convert that into miles per gallon, which effectively makes miles per gallon irrelevant.

GM says the EPA will weight plug-in electric vehicles as traveling more city miles than highway miles on only electricity, presumably figuring that people buy electric cars primarily for local driving. GM expects the Volt to consume 25 kilowatt hours per 100 miles in city driving. At the U.S. average cost of electricity , a typical Volt driver would pay about $2.75 for electricity to travel 100 miles, or less than 3 cents per mile.

Also, if you use the electric vehicle’s or hybrid’s electric-only mode, the miles per gallon are “infinite or have no meaning since no gas is being consumed,” according to Anthony Eggert of California’s Air Resources Board . Of course, it does take oil, coal, nuclear, wind or hydro power to create the energy electric cars are powered on, so even eco saints don’t get off free. To complicate matter further, if you want a hydrogen fuel cell-powered vehicle, like a Honda FCX Clarity, you will need to measure mileage in MPKs, or miles per kilograms of hydrogen. The Clarity gets roughly 60 miles per kilogram.

Eggert is in charge of science and technology policy for the state agency, which sets green house gas performance standards and develops “miles per gasoline gallon equivalents” for electric and hydrogen fuel cell vehicles so it can rate the amount of harmful CO2 released into the air.
It’s all very confusing and is likely to get even worse, according to Eggert, who doesn’t “even bother” with GM’s 230 MPG claim. “We ignore such claims entirely,” he says. “We look at total energy consumed so we can figure out how much greenhouse gas is being emitted into the air.” That is, the industry may be moving from miles per gallon to miles per bucket of soot, or in ARB’s case grams of CO2 per mile. In the case of a Ford Explorer, for example, ARB rates it at 400 grams per mile for greenhouse gas emissions. A Toyota Prius is rated at 200 grams per mile.

The new carbon emission ratings are destined to be part of our car buying futures. Now it’s up to ad agencies to make these new performance metrics sounds sexy.

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