“now runs on E15 which is 85% unleaded gasoline and 15% ethanol.”
Why?
In NASCAR, nobody rides for free.
Why?
MONEY!
NASCAR has been hit on two fronts by the economic down turn. Attendance at the tracks and a shortage of sponsors for NASCAR and the car owners.
NASCAR made the American Ethanol partnership announcement just weeks after announcing a switch in its major national series to Sunoco Green E15, a new 15% ethanol blend fuel made with corn grown in the United States. (The 2010 February Daytona Race was the first race to use E-15 as fuel)
Financial terms of the six-year agreement were not disclosed.
The ethanol industry was pushing for the federal mandate that was 10% ethanol to be increased to 15% ethanol in the "gasoline" you and I buy. The deal with NASCAR was advertising to promote E15.
In December of 2011 The US House of Representatives voted against increasing the mandate from E10 to E15. At the same time they stopped the 45 cents per gallon federal subsidy for ethanol.
NASCAR and E15, it was one of those follow the money trail things. NASCAR needed money, the ethanol industry had the money and needed positive advertising to get their mandate.
It didn't happen.