Paul Mathieson was found with serious injuries in Houston Street, close to Wilson St, on 14 January.
He was taken to the Queen Elizabeth University Hospital, but died six days later.
Officers launched a murder inquiry following the death.
Police want to speak to the driver of the Mazda car seen around 12:15 on 14 January in Hairst Street and Renfield Street. The vehicle then turned into Wilson Street and continued its journey on the one-way system round to Fulbar Street.
Detective Chief Inspector Martin Fergus said: “Paul died following a violent assault and it is imperative we find his killer and hold them to account for their actions.
“The person or persons within the silver Mazda 2 car may have seen something that can help us in our enquiries and we would urge anyone driving a car matching the description to come forward and contact us.
“I know some people may think they don’t know anything which could help us or they think they didn’t witness anything, but we need to know who was in the area and who Paul saw and spoke to that evening and your information could contribute to that.
“Let us be the judge of how relevant the information is. We are gathering information from a number of sources and one small detail could prove pivotal in piecing together the events of that evening and therefore leading us to trace the person responsible for this young man’s death.
“We have already traced a number of people who were seen on CCTV that evening, but I would like to reiterate that there are still some people on CCTV footage who have yet to contact us and I would urge them to get in touch.”
Anyone with information is asked to contact officers from the major investigations team based at Paisley Police Station on 101 or via Crimestoppers on 0800 555 111.