Last Sunday afternoon, after finishing my dance class, I passed by a gas station and took another look at the price board. I couldn't help but think that this number wasn't the same as it was just a month ago.

Even the seniors in my group, who usually chat over a cup of coffee after class, have started their conversations with discussions about gas prices these days. I took some time to sort out why they have risen and when it might be less painful to fill up.

The issue began on the afternoon of September 13. The ExxonMobil Joliet refinery near Joliet experienced a power outage due to a storm, causing the entire plant to shut down.

While power was restored that evening, they couldn't restart operations immediately. Reports indicated that the pumps, which were dealing with the flooded water, couldn't handle the situation, leading to delays in restarting.

This refinery processes 275,000 barrels of crude oil per day. It produces nearly 11 million gallons of gasoline and diesel daily, making it a crucial supplier for the Chicago area.

The fuel produced here travels through pipelines not only to Illinois but also to Indiana, Wisconsin, Michigan, and Ohio. When one facility goes down, it shakes the entire Midwest.

Articles from mid-September reported that diesel prices in Illinois jumped by 47 cents in just a week. With diesel hitting record highs nationwide, it was hard not to be surprised.

Fortunately, ExxonMobil announced that the refinery was fully operational again by the end of September. It took just over two weeks for it to regain its rhythm.

So, have prices come down now? According to AAA's data from October 4, the average price for regular gas in the Chicago metro area was $4.754 per gallon.

This is about 13 cents lower than the $4.888 from a week ago. However, compared to a month ago when it was $4.458, it is still nearly 30 cents higher.

A year ago on the same day, the average in the Chicago metro area was $3.485. This means that in just one year, the price has increased by $1.27 per gallon, leaving me momentarily speechless.

The average for the entire state of Illinois on the same day was $4.672, while diesel was at $6.694. Those who operate trucks or diesel vehicles are likely feeling the pinch even more.

Why do prices take so long to drop even when the refinery is back online? Gas stations tend to quickly raise prices when wholesale costs go up, but they are cautious about lowering them.

Additionally, this year has seen complications from Middle Eastern tensions and international oil price pressures. It seems unlikely that prices will return to last year's levels just because one refinery is back in operation.

So, what can we do? We can choose our timing. GasBuddy's analysis from February this year was quite useful.

According to this analysis, the best day to fill up in Illinois is Sunday. Conversely, prices tend to be highest around Wednesday.

Nationally, prices start to rise on Monday, peak midweek, and then gradually decline as the weekend approaches. It's like a waltz, with a rhythm of rising and falling throughout the week.

In most states, the difference between the cheapest and most expensive days is between 4 to 9 cents per gallon. While it may not seem like a lot at once, it adds up over the year.

In states like Indiana and Michigan, where prices fluctuate significantly, the difference can range from 15 to 45 cents. If you frequently travel near state borders, it's worth comparing prices.

This is what I've been doing lately. On my grocery runs on Wednesday evenings, I just pass by unless the gas warning light comes on.

Instead, I fill up generously on my way back from class on Sundays. By refueling before my tank runs low, I can avoid rushing into expensive stations.

There are days when gas prices vary quite a bit even within the same area. Just checking a few nearby gas price apps before heading out can ease my mind.

On days when prices spike dramatically after a refinery incident, it's also a good strategy to only fill up what you absolutely need. It's better to wait a few days until prices stabilize before filling up completely.

Your driving habits also play a significant role. Reducing rapid starts and stops and ensuring your tire pressure is correct can help you go a bit further on the same amount of gas.

In my senior group, more people are organizing carpools for events these days. Even with just three people in one car, the gas costs are shared, and the conversations along the way are a bonus.

I've cut back on evening sunset drives. While it's a bit disappointing, enjoying a cup of tea at home while listening to Debussy instead of watching the sunset outside isn't so bad either.

While we can't control gas prices, we can choose when to fill up. Taking it easy and pacing ourselves applies both to dancing and to stopping at the gas station.

If it were up to me, I would choose to fill up on Sundays for the time being and just compare prices during the week. I hope you have a relaxed stroll in front of the gas station this weekend.