Yup, my car does about 25 MPG so I would have to do about 60,000 miles on my FZ6 for it to pay for itself and that's not including maintenance and insurance.
If I really wanted to save money, I would sell my pretty new car and pick up a winter beater. I could use the bike as reliable transportation as long as it's above 40 degrees out and then my $1,000 jalopy when it's snowing. As it stands I would pretty have to not drive my car during riding season for the next ten years to hit 60,000 miles in just commuting.
Now if my car got 15 MPG it would only take about 24,000 miles to recoup the cost of the bike.
The crazy thing is the bump from a 45mpg bike to a 65mpg bike would only save $300 / 12,000 miles, but a bump from a 15 mpg car to a 25 mpg car saves $1,200 / 12,000 miles. So getting a more fuel efficient bike than the FZ doesn't even really help this scenario.
I do this for a living, so I'v tried to crunch the numbers every possible way, the only conclusion I come to (if I want to save money) is to sell my car.
But I digress.... we were talking about tires right?