Really glad you posted this one - I have been meaning to do something similar for ages.
I have a 15 year-old Toyota Corolla with 120k on the clock (the last 70k of which were mine). The only times it has ever let me down were not down to Toyota parts (battery failure, and alarm immobiliser failed after I had left it for 3 months on the drive).
Anyway, it averages 33.55 MPG and I do most of my own servicing (not the complicated stuff!) so running costs are pretty low. I had a Toyota Prius as a hire car from work a while ago, and I worked out that I could save myself £1.72 a day in fuel if I bought one of them, so even with a couple of grand off the asking price for the Prius, it's still a no-brainer for me.....
As for the environmental impact, I would take a lot of convincing before I believed that buying new, 'eco friendly' cars had less impact than keeping my current one.
Only trouble is, it does lack a little street cred
