(NEXSTAR) – As gas prices remain high – and are expected to rise even further – you may be looking for ways to save money at the pump. How can you tell if you should fill up on gas now or wait for prices to drop in a few days?

It’s pretty easy to predict when gas prices are about to rise, said GasBuddy’s lead petroleum analyst Patrick De Haan. All you have to do is watch the price of oil.

“That’s a good indicator of where prices may go in the days ahead … simply because oil is the main ingredient in gas,” said De Haan.

If the price of a barrel of crude oil starts to climb, you can expect to see the price of gas follow suit. But the impact isn’t immediate, De Haan said, so you have time to react and fill up your SUV or minivan before prices spike. Just how much time you have varies, but it’s usually about three to five days before oil price changes are reflected in gas prices.

“If the price of oil was to jump $20 a barrel today, [gas] stations may look to pass it along as quick as possible because it’s so significant,” he explained. “But generally it takes a few days for oil prices to pick up steam. Gas stations are probably not able to successfully pass along [oil price increases] for at least a day.”

Other ways to save money at the pump include making sure you’re filling up on the cheapest days of the week and to shop around. Comparing prices between gas stations in your neighborhood can save you money in the long-run.

“Prices can vary significantly from block to block,” De Haan said. “You can save $100 or even $200 to $300 over the course of the year if you’re paying attention.”

The average gas price nationwide is about $3.30 a gallon, according to AAA. California has the highest prices in the country with an average of $4.66.