At 250 million cars, that 60 years is down to 14, which doesn't sound quite as impressive.

Nobody knows what the crisis of high fuel prices will get the number of cars down to. the number of cars is not that relevant it's how many are on the road at a given time and etc.

If the number of cars isn't relevant, then why would the person saying "60 million for 60 years!" mention them?

Point is, it's a dodgy claim.