SIOUX FALLS, SD - South Dakota fleet officials are experimenting with a lower ethanol blend in the state's flex-fuel vehicles in hopes of determining the most cost-effective blend available, the Associated Press reported.

Preliminary tests indicated E85 wasn't saving the state money, so state pumps in Rapid City, Sioux Falls and Pierre are now dispensing E30 as part of a year-long test to find the optimum blend of fuel. The goal is to find a blend that provides the best mileage at the best cost, said Mike Mueller, spokesman for the Bureau of Administration.

South Dakota's 1,290 flex-fuel vehicles account for 37 percent of the state's fleet of 3,442. The state has been purchasing flex-fuel vehicles whenever possible to support the renewable fuels industry.

The E85 tests ran through the end of June. Tests on the 30-percent blend will run through the end of 2010.

E85 was 23 cents per gallon cheaper than the standard 10-percent ethanol blend, but tests showed that the 23-percent decrease in gas mileage negated the cost savings. The net result was a 1.49 cent cost-per-mile operating increase in the E85 vehicles, Mueller said.

A spokesman for ethanol producer Poet, Rob Skjonsberg, told AP that Poet favors an open fuel market and consumer choice through the availability of blender pumps. Such pumps allow motorists to select the amount of ethanol in their fuel -- from 10 percent up to 20, 30 and 85 percent ethanol. He added that recent studies indicate that midlevel blends -- E20 to E40 -- are the most cost efficient.

The Bureau of Administration hopes the test will determine which blend level gives the best mileage at the best cost.