A mysterious viral advertising campaign has surfaced on television and the Internet this week, which has been further amplified over the blogosphere.  In fact, , facebook , YouTube , and blog sites have surface around it.

A simple green background shows the number 230, with a winking electric outlet instead of the zero. Below is the date 8-11.

AdAge determined that the source of the campaign is none other than GM, but the automaker and its ad agencies won't say what it means.

Speculation has varied on its meaning from the MPG of the Buick plug-in to the MPG of the Volt or even something to do with charging at 220V.

GM is holding a press conference in Detroit on August 11th, and yes I will be there.

Reports quote sources as saying the number will be the Volt's official MPG rating, but how they came to it remains a mystery; highway, city, average, none of the above?  And if so how was it calculated?  The EPA city cycle is 11.04 miles, the highway cycle is 10.26 miles.  The car goes 40 mile without any gas, and 78% of drivers drive less than 40 miles per day (utility factor).  Do your own math.

Here's my guess:

I heard of a method to determine the MPG of an EREV; first the car is driven from a full battery until it reaches charge-sustaining mode, then one more cycle is driven. If we use the highway schedule, the first 40 miles are electric.  One more cycle is 11 more miles. If the Volt gets 50 MPG in charge sustaining mode, it will use .22 gallons of gas for that 11 miles.  Thus 51 miles/.22 gallons = 231.8 MPG.

We can have fun guessing for now, but be sure to logon to GM-Volt.com on Tuesday morning and we will have the answer as soon as it hits.

Plus, if you have any questions you want me to ask the Volt team and execs while I am there, leave them in the comments.

Source ( AdAge )

[UPDATE:  The method referred to to measure the efficiency of an EREV is far more complex and still under development.  Though my calculation came out similar the methodology GM actually used to determine the MPG was different.  See this post .]