Regular unleaded gasoline is regular unleaded motor gasoline with an 87 to 88 octane. Midgrade gasoline is motor gasoline with an 89 to 90 octane, which includes some octane boosters (this includes E-10 in Nebraska). Premium gasoline is motor gasoline with a 91 and higher octane. Diesel fuel is fuel used for internal combustion in diesel engines.
A general rule of thumb: A dollar increase in the West Texas Intermediate (WTI) crude oil price will result in a 2.5-cent increase in the prices of gasoline and diesel fuel. Likewise, a dollar decrease in the WTI crude oil price will result in a 2.5-cent decrease in the prices of gasoline and diesel fuel.