Fadi Fawaz, 44, said they used to sing their favourite songs together inside it.
But the fine art photographer said the memories the motor evoked were too painful to bear.
He found the 53-year-old Wham! performer’s body at home in Oxfordshire on Christmas Day 2016.
Fadi had slept in the car the night before.
“It’s all a bit much to handle”
He tweeted: “Selling my car that George gave me as Xmas gift. “I will put a picture of it later so if anyone interested let me know pls.
“I have not mentioned the surprise that comes with the car. The reason I’m selling is because of lots of memories in my car with George listening to our favourite songs him singing in the car ect ect ect (sic).
“It’s all a bit much to handle x (sic).”
Fadi called police after finding the singer dead in bed on Christmas morning.
He said at the time: “We were supposed to be going for Christmas lunch.
“I went round there to wake him up and he was just gone, lying peacefully in bed.”
Lebanese-born Fadi was reportedly banned from George’s funeral but was seen arriving at Highgate Cemetery in north London.
George’s cousin Andros Georgiou had initially said: “Fadi has not been invited to the funeral.
“He is not welcome. Fadi was not really his boyfriend.”