Gas prices always seem to be lower in the winter than in the summer. All the things that make gas prices rise and fall can be pretty convoluted, and a lot of factors play into seasonal price differences. There’s higher demand in the summer, with people going on vacations, and generally getting out more and doing more driving. The biggest factor that makes gas cost more in the summer is that the gasoline is actually different.
Gasoline isn’t just one substance. It’s a blend of different petroleum products and additives. The exact blend can vary from place to place, season to season and brand to brand. Since 1995, oil companies have had to produce different blends of gas for summer and winter, in order to comply with EPA regulations. The regulations, and the difference in the gas, have to do with evaporation of fuel.
Gasoline, just like water, can turn into vapor and escape into the atmosphere. The EPA requires oil companies to sell gas that is less likely to evaporate, between June 1 and September 15. That’s because the heat of the summer already predisposes the gas to evaporate. More gas evaporating can lead to an increase in smog. It also of course, means that you’re losing gas – and money.
Since it’s colder outside in the winter, evaporation is less of a concern and regulations on gas are less strict. To cut costs, oil companies use butane as part of their winter blend. Yes that’s the same butane that comes in Bic lighters. Butane is cheap, but it evaporates easily. These are the two features that make it an ideal lighter fuel. It also makes winter gas cheaper per gallon than summer gas. That’s a big part of why gas is cheaper in the winter.
There is one problem with butane, though. It has less energy than other petroleum products. When you buy winter gas, you literally get less bang for your buck. That’s a big part (but not the only one) of why you see reduced fuel mileage in the winter. In the end, winter gas may be cheaper per gallon, but you’ll end up using more of it. Odds are your overall fuel costs will be about the same.
So, you might be thinking, “why don’t I store summer gas to use in the winter?” (or perhaps “why don’t I stock up on cheap winter gas?”) Keep in mind that each type of gas is formulated for its particular season. The increased likelihood of evaporation makes winter gas burn better in cold weather. At the same time, if you try to run winter gas in the summer you’re going to lose some gas to evaporation. There is, after all, a reason they make different blends for different seasons.
Written by Dan Smolinsky.