Could you please tell me if it's convenient to use Western Union gasoline credit card? Or is it basically cash? How much does it cost to fill up the gas tank once ?

Domestic credit cards are not very useful for self-service gas stations in the United States!

We all use cash, go to the counter and say how much to add, and then get a refund if there's a surplus.

It is generally recommended to use cash. Credit cards take longer to refund, and you need to pay first at gas stations, for example, 50 yuan. Tell the gas pump number, then fill up, for example, 35 yuan, and you will get a cash refund of 15 yuan. If 50 yuan is not enough, you can pay more. It is not recommended to use credit cards, especially at small and remote gas stations. Additionally, unless you want to make a profit.

Petrol prices vary from place to place. It's expensive in the city. A box of Nissan X-Trail costs 40-45 dollars. For reference, I think credit cards are convenient, and you have to go to the counter twice.

If you don't have a US bank card or credit card, it's best to use cash. Gas in cities like San Francisco and Los Angeles is likely to be about $3.30 per gallon. It's uncertain around scenic spots. Yosemite National Park and Death Valley are more expensive.

Domestic V and M credit cards are preferred for pumping gas. When you go to the counter, you should say the pump number, gas type, and have $100 pre-authorized on your credit card. After pumping, I like to take a picture of the pump's numbers and then go back to the counter to request a receipt for verification. Most gas stations will settle the actual amount in 2-4 days, while a few will deduct it immediately. There are few cash discounts for gas in the western region, but there are significant discounts in Hawaii. When using a credit card, you have to swipe it yourself, but the gas station attendants are there to help.

Domestic credit cards can't go through. I always use cash to add fuel.