Jim Haggart joined the AA in Glasgow in August 1966 as a 16-year-old cadet after spotting the opportunity in a newspaper advert.
The 64-year-old has helped an estimated 87,000 motorists with car trouble - between 1,500 and 2,000 a year - around the west of Scotland, rescuing animals, young children and even babies that have been accidentally locked in vehicles.
Extensive car knowledge would seem an obvious requirement for his job but Mr Haggart said he knew nothing about them when he first started and he had to pass his driving test while on the job.
He said: "One of the first tasks as a cadet was obviously to get your licence. I took my test privately the first time and failed spectacularly.
"The second time, I went out with my old superintendent who was also an examiner - there was some pressure having the boss sitting next to me.
"I knew absolutely nothing about cars when I joined but I got trained well.
"A lot of the cadets left and I think the programme was phased out as more mechanics could do the job, but I enjoyed it so much that I stayed on."
He started his final shift today with a wheel change in the south side of Glasgow.
As well as the traditional yellow AA vans, Mr Haggart has used a BSA Bantam motorbike, an Austin Minor, a Morris Marina and a Talbot Express to get around to jobs.
The tools of his job have also changed dramatically over the years.
"It's all technical now with diagnostics," Mr Haggart said.
"We still have tools obviously, and I do wheel changes and a lot of mechanical stuff, but most things now we plug into the computer in the car and find out why certain lights are on and pick out the faults."
He laughed as he said: "When I first started I basically had a tool box with a couple of spanners, a couple of screwdrivers, a gallon of petrol and a jack - that was it.
"Cars themselves have changed beyond all recognition, people even tell me they're frightened to lift the bonnet now.
"Guys years ago who were willing to change the plugs in their car can't even find the spark plugs in modern cars nowadays."
The AA say Mr Haggart has driven about 1.4 million miles and rescued around 87,000 people at the roadside over his 48-year career, and it has been a rewarding experience for the mechanic.
"People panic if they've locked themselves out of a car," he said.
"I've had babies locked in cars, young children, dogs - it's quite fulfilling when you can open a car if there's a baby inside it.
"I've been to jobs where the police and fire brigade are there and they can't get in to it, and I've managed to get it open, so it can be quite rewarding that way."
Mr Haggart's manager Graham Coburn said he is sad to see the long-serving patrolman retire.
"Jim is a brilliant patrol," he said.
"He is always at the top of the team in terms of performance and he's also one of the all-round nice guys.
"He always has an amusing story to tell and he is a fantastic ambassador for the AA."
Mr Haggart's wife Maureen is retiring as a librarian today and the couple plan to enjoy their time off by relaxing and taking long drives.
The AA man said if he runs into trouble he will know who to contact.
"I'll call on a colleague. If it's a wheel change I could do it, depending if I can still reach down to do it, but if it's anything else I'll need a hand."