Gas prices are now below $4 a gallon: As prices fall, here are even more ways to save money

It's finally happened: For the first time since early March, the U.S. average price of gas has fallen back below $4 per gallon, according to AAA.

Although gas prices are falling, now isn't the time to go to the pump and pay full price. From the best gas loyalty programs to expert ways to save at the pump, TPG is committed to helping you save when filling up your car.

We get it — some of these geek-like ways to save at the pump aren't always simple. So, here are several easy ways to save money on gas.

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Check nearby prices with Gas Buddy

Once described to me by an Uber driver as a "God send," Gas Buddy allows you to see recent gas prices at stations near you. Drivers can report fuel prices directly on the app, so you always know that you're getting the best price on gas.

Here's an example in Pasadena, California:

As you can see, within a small radius of my location, gas prices range between $4.89 and $6.89.

Finding the station with the least expensive gas will go a long way.

Related: How to use GasBuddy to get ahead of summer’s fuel price surge

Shell Fuel Rewards

Shell's Fuel Rewards program is an easy way to save at least 3 cents per gallon at the pump. When you sign up — which you can do directly at the pump — you'll receive instant Gold status. You'll get 5 cents off per gallon on your first fill-up. This stacks with any additional Fuel Rewards you earn — all the way up to making gas nearly free.

With its own dining rewards program, shopping portal and countless national partners, one TPG staff member saved over $2,000 with Fuel Rewards.

Also, when you link your Dunkin’ Donuts rewards account, you can earn an additional 10 cents per gallon. Or, eat at your favorite local restaurant in the dining rewards program and earn 10 cents per gallon.

Those savings combined with your Gold status will make your next fill-up at least 30 cents less per gallon. All Fuel Rewards fill-ups are capped at 20 gallons. Once you start pumping, your savings are used, whether you pump one gallon or 20.

If you want to earn American Airlines Loyalty Points towards AAdvantage status, you can opt to earn 2 American AAdvantage miles per gallon purchased, instead of cash back at the pump. TPG values AAdvantage miles at 1.77 cents each. So at 2 miles per gallon, you’ll earn 3.54 cents for each gallon of gas (though there are sweet spots where you can get far more value).

All you have to do is enter your phone number at the pump before filling your tank.

T-Mobile

Select T-Mobile customers can save 25 cents per gallon at Shell stations through the week of Labor Day.

The carrier's infamous T-Mobile Tuesdays give customers 25 cents off per gallon at Shell stations. “To help take the sting out of rising gas prices, T-Mobile teamed up with Shell and the Fuel Rewards® program to give customers an exclusive 25 cents off per gallon of gas this summer through the week of Labor Day via T-Mobile Tuesdays," according to the company.

Ultimately, this perk has been a great way to save on gas, though it's scheduled to end in about three weeks. It's worth seeing if your plan includes this perk.

Related: Credit cards that cover cell phone loss and damage

Kroger Plus

Kroger owns a huge percentage of America's grocery stores. Even if there isn't a Kroger-branded grocery store near you, it's worth looking into how Kroger can save you money at the pump. With a free Kroger Plus card, you can get up to $1 off per gallon at gas stations in the company's network (including most Shell stations) just with your weekly grocery spending.

To learn more about the Kroger Fuel Points program, check out the website.

Related: Saving on gas: Everything you need to know about fuel loyalty programs

Use the right card

It's important to know which card to use at the pump. After all, using the right card can get you upwards of 5% back. Here are some of our favorites.

From July 1 to Sept. 30, Chase Freedom (no longer open to new applicants) and Chase Freedom Flex cardholders can earn 5% cash back (or 5 points per dollar) on up to $1,500 in fuel purchases.

Another great option is the Citi Premier® Card which earns 3 points per dollar on gas purchases — a 5.4% return at TPG's valuations. You can transfer Citi ThankYou points to a variety of airline and hotel programs to maximize their value.

If cash back is more your thing, the Costco Anywhere Visa® Card by Citi earns 4% back on gas, and EV Charging purchase (up to $7,000 annually). You can use your Costco Anywhere Visa at any gas station. Plus, you'll have access to Costco's pumps, which generally have some of the lowest fuel prices.

Related: Best credit cards for gas purchases

Bottom line

Fortunately, gas prices are finally beginning to decline. Still, I'm going to be working just as hard to maximize my rewards at the pump.

By using Gas Buddy, maximizing your station's rewards program and charging your purchase to a generous gas-earnings card, you stand to save a tremendous amount on your fill-up.

That definitely beats paying full price.