Police are offering some tips to protect yourself from this growing trend.
LOWER MERION TWP., Pennsylvania -- Drivers are being warned about pump switching, a gas station scam that's become a growing trend.
Police in Lower Merion Twp., Pennsylvania said they have seen a recent uptick in the crime.
They said it occurs when an aggressive suspect offers to help someone pump gas.
"The suspects are often very aggressive and outright refuse the victim's attempts to deny assistance," Lower Merion Twp. police said in a Facebook post.
The victim leaves, but the scammer doesn't return the nozzle to the pump.
Instead, the scam artist uses the active transaction to pump gas for other drivers, while demanding cash for gas.
"They'll say, 'Hey, I'll pump your gas. Give me $20, I'll fill you up,'" said Det. Sgt. Michael Keenan. "They'll just charge it until the pump stops working or the credit card fills up."
The suspects then keep the cash and leave the gas station, police say.
Police say most victims don't realize the crime has happened for days or weeks after the incident, which makes it difficult for law enforcement to find and prosecute the offender.
To protect yourself, police recommend hanging up your own gas nozzle to end the transaction and print a receipt.
If you think you've fallen victim, Keenan advises you, "Pull off to a safe distance. Call 911 if you're close by or near the gas station. Wait for someone to get there, point out who took your gas handle or who you think is scamming you."
Investigators say this crime pops up from time to time, and they put out a warning after seeing an uptick again along City Avenue, the township's border with Philadelphia.
But, Keenan told Action News this is a crime that "happens everywhere."
Police say they have identified at least one suspect who could be involved in the recent uptick in Lower Merion Township. They say that person has been involved in similar incidents in the past.
Anyone who is experiencing pump switching should call 911.
Susan Mancill told Action News she was filling up on the corner of Conshohocken State Road and City Avenue on the afternoon of Sept. 9 when she was approached.
"I was automatically approached by someone asking if they could pump my gas. I said 'Nope, I'm good. Thanks.'"
Feeling uneasy, Mancill filled her car with a few gallons and decided to leave.
"As I was getting ready to put the pump back in, he came around and took the pump out my hand and said 'Hey! Don't worry about it, sweetheart. I got it.'"
After driving away, Mancill said she later got a notification from her credit card company that she had been charged $165 for gas, not the $35 she thought she had spent.
After seeing the Facebook post from Lower Merion Township Police, Mancill realized she was a victim of the pump-switching scam.
She has since reached out to her credit card company and they have agreed to only charge her the $35 she spent on gas.
Her advice to other drivers is: "If you're driving around looking for gas, look in the station and see if you see any people soliciting."
"If I could go back, I would call 911 right away like police recommended," Mancill said.