"Wash the car" is a common way to say "洗车" in Engpsh. Other phrases you might use include:

"Give the car a wash"
"Clean the car"
"Wipe down the car"

You can also use more specific phrases, such as:

"Rinse the car" (将车喷水清洗)
"Suds up the car" (用肥皂清洗车)
"Dry the car off" (擦干车)

For example:

"I'm going to wash the car this weekend." (我这个周末要洗车。)
"Do you have time to help me clean the car today?" (今天你有时间帮我清洗车吗？)
"I'm going to rinse the car off before I dry it off." (我要先用水清洗车，然后再擦干。)