The McLaren driver, a two-time Formula One world champion, began his career in cars as the proud owner of a humble Renault Megane.
The workaday motor was a sponsor's gift when the former karting world champion was cutting his teeth in Formula Three in Spain.
"It was yellow, yellow-brown," Alonso told CNN's The Circuit.
"I was happy. When you are 18, whatever car someone gives you at that moment -- you are super happy."
However, the Spaniard didn't treat the Megane with the same love he shows his Formula One cars today.
"I was not as good a driver then," said the 36-year-old.
"I wasn't doing crazy things, but I wasn't taking too much care over the car.
"It only got cleaned it when it rained."
Testing times for Alonso
Alonso made his F1 debut with Minardi in 2001 and went on to win two world titles with Renault in 2005 and 2006.
But he has endured a difficult few seasons since joining McLaren in 2015 after a four-year spell with Ferrari.
Mechanical issues have forced him out of five races so far this season, with the only highlight a sixth place at the Hungarian Grand Prix to leave him 15th in the drivers' standings.
Alonso hasn't made a decision about his long-term future in the sport, but feels he has "unfinished business" with McLaren.
"Everyone will have their opinion about what we need to be competitive," says Alonso.
"I have mine, which I will not share now. If that happens, I will consider, for sure, to stay and win with McLaren.
"I need to see some numbers, some hopes to touch, not only dreams for next year, and all the expectations we have already.
"We have too many expectations -- now it's time to make it real and to show the potential that we all think there is behind this partnership."
Alonso missed this year's Monaco GP to compete in the Indy 500 where he was forced to retire with 21 out of the 200 laps remaining.