Smith, from Washington state in the US, kept quiet about his secret fetish for years, but agreed to be interviewed as part of a documentary into “mechaphilia”.
A major newspaper quoted him, as saying: "I appreciate beauty and I go a little bit beyond appreciating the beauty of a car only to the point of what I feel is an expression of love."
He added: "I'm a romantic. I write poetry about cars, I sing to them and talk to them just like a girlfriend. I know what's in my heart and I have no desire to change."
He said: "I'm not sick and I don't want to hurt anyone, cars are just my preference."
Smith, 57, first had sex with a car at the age of 15, and claims he has never been attracted to women or men.
He says his most intense sexual experience was "making love" to the helicopter from 1980s TV hit 'Airwolf'.
Apart from Vanilla, he regularly spends time with his other vehicles – a 1973 Opal GT, named Cinnamon, and 1993 Ford Ranger Splash, named Ginger.
Before Vanilla, he had a five-year relationship with Victoria, a 1969 VW Beetle he bought from a family of Jehovah's Witnesses.
He confesses that many of the cars he has had sex with have belonged to strangers or car showrooms.
His last relationship with a woman was 12 years ago - and he could not bring himself to consummate it, although he did have sex with girls in his younger days.
Talking about how his unusual passion developed, Smith said: "It's something that grew as a part of me when I was a kid and I could not shake it."
Smith is now part of a global community of more than 500 “car lovers” brought together by internet forums.