A little more than a year ago, oil prices were above $100 a barrel. The national average for gasoline was in the $3.50 range. In late spring, oil was $60ish and the national average for gas was around $2.70. The price of a barrel of oil has plunged to $40 and below-yet, prices at the pump are just slightly less than they were when oil was almost double what it is today.

Oil and gasoline prices usually travel up or down in sync. But a few weeks ago the trend lines crossed and oil continued the sharp decline while gasoline has stayed steady-even increasing.

Oil's down, gasoline isn't. Consumers are wondering: "What's up?"

Even Congress is grilling refiners over the disparity.

While, like most markets, the answer is complicated, there are some simple responses that even Congress should be able to understand. The short explanation is "refineries"-but there's more to that and some other components, too.

Within the U.S. exists approximately 20 percent of the world's refining capacity. Fuel News explains that "on a perfect day," these domestic facilities could process more than 18 million barrels of crude oil. But due, in large part, to an anti-fossil fuel attitude, it is virtually impossible to get a new refinery permitted in America. Most refineries today are old-the newest major one was completed in 1977. Most are at least 40 years old and some are more than 100. Despite signs of aging, refining capacity has continued to grow. Instead of producing at 70 percent capacity, as they were as little as a decade ago, most now run at 90 percent. They've become Rube Goldberg contraptions that have been modified, added on to, and upgraded. The system is strained.

To keep operating, these mature refineries need regular maintenance-usually done on the shoulders of the busy driving seasons and when systems need to be reconfigured for the different winter and summer blends. Even then, things break. Sometimes a quick repair can keep it up and running until the scheduled maintenance-known as "turnaround." Sometimes, not. Fixing the equipment failures on the aging facilities can take weeks.

This year, several unexpected maintenance issues happened in the spring. Other refineries worked overtime to make up the shortage. That, plus low crude prices, means that many refiners didn't shutdown for the usual spring turnaround. Fuel News notes, potential profit encouraged refiners to "get while the getting's good."

This pedal-to-the-metal approach is catching up with the sagging systems. On August 8, BP's Whiting, IN, refinery, the largest supplier of gasoline in the Midwest, faced an unplanned shutdown due to a leak and possible fire hazard in its Pipestill 12 distillation unit-which processes about 40 percent of its 413,000 barrel per day capacity.

The closure of the largest of Whiting's three units caused an immediate jump in gasoline prices in the Midwest. Stockpiles were drawn down to fill demand during summer's peak driving season. Gasoline has been moved-via pipeline, truck, and train-from other parts of the country to balance out supply. So, while the biggest price increase was in states like Minnesota, Michigan, and Illinois, prices raised nationwide beginning on August 11.

Meanwhile, because the Whiting plant wasn't sucking up crude oil, its supplies grew and drove crude prices down further-hitting a six-year low. The Financial Times reports: "An outage at Whiting's main crude distillation unit could add almost 1m [million] barrels to Cushing [The OK oil trading and storage center] every four days as long as it is out."

Making matters worse, another Midwest refinery, Marathon's Robinson, IL, 212,000 barrels per day facility is down for repairs that are expected to take two months.

Other smaller outages include Philadelphia Energy Solutions and the Coffeyville Resources' refinery in Kansas. BloombergBusiness states: "As many as seven other Midwest refineries could shut units for extended time this fall." Though, other reports indicate that some of the planned maintenance may be put off due to profit margins that are at a seven-year high.

Adding to the price increases due to refinery issues, are two other factors-both having to do with the calendar.

First, we are almost to Labor Day, which is considered the end of the summer driving season. It is when families make that one last trip to the lake or to visit grandma-which always causes a jump in demand that tightens supplies. This year, with two big refineries down, the usual spike could well be exacerbated.

The other is hurricane season. While we are just past its peak, we've only had one hurricane so far: Hurricane Danny-which last week was barreling toward the Northern Caribbean islands, with potential to hit the refinery-rich Gulf Coast. On Friday August 21, it moved from Tropical Storm Danny to Category 3 Hurricane status. It has since weakened, but its presence caused risk and supply concerns.

High summer-driving demands and unscheduled refinery repairs have combined to reduce supply of gasoline, and raise the price, thus the need for crude oil-especially in the Midwest-is down. Crude oil inventories at the Cushing hub continue to increase and add to the current oversupply and slide in oil prices.

While there's some other contributing factors, the current mix of supply and demand explains: "what's up?" The lack of new refineries punishes the whole system. Gasoline prices are up-hurting consumers. Crude prices are down-hurting producers.

The author of Energy Freedom, Marita Noon serves as the executive director for Energy Makes America Great Inc. and the companion educational organization, the Citizens' Alliance for Responsible Energy (CARE). She hosts a weekly radio program: America's Voice for Energy-which expands on the content of her weekly column. Follow her @EnergyRabbit.