National average gas prices are forecasted to be a quarter a gallon less expensive than in the summer, according to AAA. The forecast indicates the national gas price average will drop to $2.70 this fall, with the potential to drop even more. This is more than a quarter cheaper than the year’s recorded high in May of $2.97 a gallon.  

Gas prices in 2018 have been higher than 2017, and the year-to-day average gas price is 41 cents more ($2.73).   

Year-over-year trends include: 

Top ten states with largest difference in gas price averages are mostly on the West Coast, Northeast or Mid-Atlantic states: 

California (+57 cents) 

Hawaii (+54 cents) 

Indiana (+49 cents) 

 Arizona (+48 cents) 

Oregon (+46 cents)  

Connecticut (+45 cents)  

Rhode Island (+45 cents)  

Utah (+45 cents)  

Massachusetts (+44 cents). 

Four Great Lakes and Central and one Southern state carry the smallest year-over-year difference in gas prices:  

South Dakota (+37 cents)  

Missouri (+37 cents)  

Louisiana (+36 cents)  

Iowa (+36 cents)  

Nebraska (+35 cents) 

The drop in gas prices this fall is due to the switch to the winter-blend gasoline in mid-September. The difference between summer and winter blends has to do with the Reid Vapor Pressure (RVP) of the fuel, which is a measure of how easily the fuel evaporates at a given temperature. A higher RVP evaporates more easily. The winter-blend gas is cheaper to produce and has a higher RVP because the fuel has to be able to evaporate at low temperature for the engine to operate properly.