With summer winding down, so too do the air temperatures, which brings a change the gasoline that Americans burn. In many areas across the U.S., summer fuels programs are going to begin concluding, meaning "winter gasoline" will soon begin to show up, and with it, potential relief at the pump.

The big day is September 15. That's when EPA relaxes its requirements across much of the U.S. for cleaner burning fuels. Summer gasoline burns cleaner, and generally costs more to produce- an expense that's passed on to motorists across the country. Reverting back to winter gasoline generally means cost savings and lower gasoline prices.

With the onset of winter gasoline comes a change in fundamentals as well- cooler temperatures and a return to the school year mean gasoline demand starts to cool. And with it, refineries begin seasonal maintenance. Generally, gasoline prices are at their lowest during these off demand times of year.

Diesel consumers may notice the opposite soon to take hold. As temps cool, those who dwell in the Northeast U.S. begin filling their home heating oil tanks. Heating oil and diesel are very similar heavy oils, and the peak consumption for this type of fuel is in the winter months. As demand climbs for the winter, so too, do the price of these fuels.

But for those who don't consume diesel, relief should be coming in the next several weeks, most likely in mid and late September as winter gasoline starts flowing.