The phrase "car number" is correct and may be used in written English.
You can use it when you need to refer to the number assigned to a specific vehicle. For example: "My car number is 5678."
I'm now on car number three.
In the olden days, convicts made car number plates.
The odd car number plate guy is about it.
Adam's crew members wore dark polo shirts with his car number, 45, embroidered on the sleeves.
In Nascar race-calling, is the car number more important than the driver's name?
"You see the 24 team," Jeremy Mayfield said, referring to Gordon by his car number.
He said he'd never liked it, but it was on his car number plate' - Jamie Redknapp.
Elsewhere, personalised car number plates are considered an amusing accessory or a mark of distinction.
His car number is 09, which is as ignominious as a football player getting a jersey with three digits.
By the time I finally set off in car number two it was dark, and still pouring with rain.
WORKERS in the sparkling new General Motors factory in Shanghai swarm around car number 337, a white Buick GL.
