I was a porter (car cleaner) at Chevrolet back in the 90's. New cars came in with plastic wrap in the interior. They did not arrive with "new car smell". That smell comes from the deep carpet cleaner we used on new car sells. It took about 2 hours and two men to clean a new sell to perfection. The carpet cleaner we used came in a white vat that was referred to as "Gosh" by the jefe. Can this carpet cleaner be purchased? I want to get the new car smell.
There wasn't anything I could find referenced to as "Gosh". What most car dealerships are doing is steam cleaning, with pre treatments and a bunch of vaccuming.
I use to help out at a used car lot. What they did to reintroduce that "new car smell" to older vehicles was spray Windex on the carpet and vigorously rub (the boss called it burning in). While that might not be the best approach for longevity of the carpet, it did work.
There are some odor neutralizing products out that work really well, provided you follow their instructions. One such product I have heard alot of good things about is Odoban (http://www.odoban.com/), no I am not endorsing, selling, working or anything related -just passing information.