Mark Francis, 44, of Resolven near Neath, had been told he would lose his vehicle later this month as he had been reassessed as no longer eligible.
David Cameron promised to look into it after Neath MP Peter Hain raised the issue at prime minister's questions.
The Department for Work and Pensions said it had received "new evidence".
Mr Francis told BBC Wales his hereditary spastic paraplegia had worsened, but he had been reassessed to a lower level of benefits in which he was no longer eligible for a car under the Motability scheme.
He said he had phone calls from Motability and the Department for Work and Pensions (DWP) on Thursday to tell him his case had been reassessed again - in his favour - after it was raised in the House of Commons on Wednesday.
"It's great that I can keep the car - too bad I only got it by getting Peter Hain to ask questions in Parliament," he said.
"How many other disabled people haven't done that?"
Mr Hain is trying to find out the reason for the change as he believes other people on disability benefits may be affected by changes to the regulations.
A DWP spokesman said: "If claimants disagree with a decision then they can seek to have it reviewed and submit new evidence.
"Mr Francis followed this process and when the new evidence was taken into account was awarded a higher rate of benefit.
"This enables him to retain his Motability car."
A disabled driver who faced losing his car under benefit changes said he was "elated" to have won his case after it was raised with the prime minister.