Some of that road has been traversed at high speeds at the wheel of a Formula One car en route to three world championships. Most of it in recent decades has been spent in the fast lane of high finance.
He readily admits he has earned more in business than he ever did squeezed into a hi-tech can careering around a racetrack.
At 72, his beginnings at the family garage may seem a long way away, but Stewart retains both a Scottish burr and a Caledonian canniness. He applies both brilliantly to an examination of why his countrymen prove so adept at manoeuvring cars at high speed and why Rangers are crashing before the very eyes of the football world.
Stewart, winner of 27 grands prix between 1965 and 1973, is one of a clan of Scots who have excelled in motor racing. He was preceded by Jim Clark, the winner of world titles in 1963 and 1965 but who was killed on the track at Hockenheim, Germany, in 1968. He has been followed by David Coulthard, winner of 13 grands prix, Dario Franchetti, the Indycar champion, Allan McNish, a two-time winner of Le Mans, and Colin McRae, the world rally champion.
Paul di Resta, the 26-year-old from Bathgate, now sits, engine revving, on the start line to what many will predict to be F1 greatness.
So why do Scots lead the way in the most frantic of races?
''We're canny, we're risk conscious,'' said Stewart, in Glasgow to promote the work of Dyslexia Scotland.
''Scots generally try harder because, for some reason, we have an inferiority complex. I think when you go down south you think everyone's going to beat you. You try harder. That complex lives through.''
Stewart warms to his theme. ''All the big bankers in the Middle East have come through Scottish education. All the traders were Scottish. Glasgow's universities were the deliverers of accountants,'' he said.
The knight of the realm then delivers the coup de grace. ''Scots are more determined, more aggressive. We haven't missed a decent war.'' And, he might have added, we have started the odd one.
This mixture of carefulness and belligerence has been spotted by Stewart in Di Resta, who is driving for Force India in this year's F1 Championship.
''Paul is very canny, he's not lost his Scottish tongue. He doesn't try to be someone he's not. Paul's a good boy. Solid, a touch too tall,'' said the diminutive Stewart, with a smile, of his 6ft countryman.
''Paul's done very well and has all the makings of a really good driver. Only time will tell just how good. It's too early to be asking too much of him,'' said Stewart. ''He's still very anxious about being able to achieve the levels people are expecting of him, whether it be the levels of Jim Clark or myself or David Coulthard. David never won a world championship but he won 13 grands prix. Stirling Moss won 16.''
He said of Di Resta: ''He has to impress a sufficient number of people so they will want him when the next good seat comes up and other drivers might not be contractually available. If he gets that I still think he'll keep his feet on the ground, I don't think he's going to get overly impressed by the privilege.
''It's easy to be distracted. You live in Monte Carlo, life isn't exactly colourless – even though they don't get as many girls as the footballers do.''
Stewart insisted, too, that Scotland's facility of producing fantastic talent was not restricted to the driving seat. Pointing to a fellow knight in Sir Alex Ferguson, he said: "Look at Manchester United's manager, still to this day angry if things don't go well.
''Who else chews gum like that? He still has a desperate need to succeed and prove himself.''
Stewart pinpoints one of the factors that drove the boy from Dunbartonshire over the finishing lines and on to podiums across the world.
''When you're dyslexic, that's what you're trying to do – be better than someone else,'' said the president of Dyslexia Scotland.
Stewart has proved to be a world-class force on the track and in the boardroom and he gave a glimpse of the principles that he carried from a Scots childhood to life as a multi-millionaire.
"I'm on the board of some big companies, like Moet Hennessy. But I can't read a balance sheet. Before I go to a board meeting, I've got to visit my accountant to find out what all of the figures are and what they mean. It's a jungle for me,'' he admitted of the effects of his dyslexia.
But one tenet has guided him unerringly through life: debt is bad.
"Modern society has come to think that debt is okay. But, in reality, we in Scotland were mostly born and brought up to not spend more than your earned or more than you could afford.
"If you were burdened by the amount of debt that accumulated over a period of time, with everyone shying away from the reality of the solution, it got into a position where it was beyond repair.
"It has happened in Greece, it is happening in the United Kingdom. I'm not political, I'm apolitical. I don't vote and I've never given a penny to a political party intentionally since I became a sports person. But debt can't be afforded. You've got to get rid of debt.''
He believes Rangers are now paying the price of ignoring what he believes is a rule of life. As the administrators of Rangers search for a new buyer in the wake of the departure of Bill Miller, the US tycoon, from the bidding process, Stewart was blunt about the causes and effects of debt.
''Rangers have built up a degree of debt that was, it seems, irreparable, particularly in the last regime. As it was going from one ownership to the next ownership, it was ignored.''
Referring to Craig Whyte who bought the club from Sir David Murray for £1, he said: ''That person said he had more money than he had and that was borrowed money. So it's a very vicious circle.
"You've got to wake up to the reality of life. A good chief financial officer would never allow that to happen and a board of directors should never allow that to happen.''
He added: ''The bottom line is this is not something only Rangers are experiencing. It is widespread. I think debt is the root of all evil, but the bankers wouldn't want to hear me say that. That's where they make their money, not by deposits.
"Sport is quite guilty of it, people trying to get things they can't afford. Common sense, and that's my experience being brought up in Scotland, would tell you not to do that. I've never had an overdraft and I don't have a mortgage.
"In all of the time with my Stewart Grand Prix team, it never had an overdraft. I had to find £32m a year to do it. It was all found. Then I sold the company for 135 times what I paid for it, with no debt.''
He said: "Scotland without Rangers would be a tragedy, the same way it would be for Celtic not to exist. Celtic and Rangers have to survive. They are the very core, an indigenous part of Scotland.''
However, Rangers will not be saved by a bid from Stewart. ''I'm only a poor racing driver,'' he said. The canniness that brought wealth and a deliverance from high-speed danger endures.