Lincoln -- Choices have changed at the gas pump, but driversshouldn't see a change in how fuel performs in their cars.
Motoristsfor many years have had a choice of gasoline fuel with octane ratings of 87regular, 89 with 10 percent ethanol or 91 premium. However, oil companies havestarted to run a sub-octane fuel up the pipeline, which is 83 or 84 octane,said John Hay, associate extension educator in biological systems engineeringat UNL.
Mixingethanol with the sub-octane fuel gives it the octane boost it needs to reach the87 octane level. Ethanol has an octane rating of 100. Fuel stations have begunto change their pumps and labels to reflect the new blends.
"Thissub-octane fuel needs to be blended with other fuel types to make it the 87octane level or above we need at the pump," Hay said. "So basically,87 with ethanol replaced the 89 with ethanol, and our low cost option at thepump is now 87 with ethanol."
Haysaid for those that used to fill up with 89 with ethanol, they can now fill upwith 87 with ethanol and it will work the same in their engines.
Beforethe changes there was about a 10-cent price difference in regular gas versusthe 10-percent ethanol blend. Since the changes, that has been ranging 15- to25-cents across the state.
"Thereason is because the 87 regular used to be just the fuel coming out of thepipeline; now it has to be blended with 91 octane premium fuel to make the 87octane regular," Hay said.
Themajority of the U.S. has already seen this change, and Hay said Midwest fuelstations will be deciding what blends to carry and what prices to charge overthe next few months.
"Theaverage car needs a minimum octane rating of 87," Hay said, but be sure toconsult your owner's manual for minimum octane required for your car.
"Totake advantage of higher octanes, you need a car with higher compressions, suchas a high-performance sports car," said Hay.
Octaneis not a rating of energy density and both the 87 with ethanol and the old 89with ethanol have the similar Btu content and will both give drivers the samegas mileage.
Aswinter approaches, oil companies will begin their annual change to"winter" fuel. This winter fuel will have the same octane but is madeof shorter chains of hydrocarbons and is thus more volatile and less energydense.
Thehigher volatility helps with cold start in winter conditions, yet has lessenergy than summer blend gasoline. This reduction in Btu content will beaccompanied by lower gas mileage but also a lower price at the pump.