Opinion - Tires, Speedometers, Odometers, and MPGs Options

[dcecc1968]

So I purchased a 914 last year that has 7-yr old Yokohama AS430's 205-50-15's, with lots of tread, but one of the tires is bad (sidewall is splitting). I'm debating whether to purchase one replacement tire or to replace all 4 (since they are all have an old manufacturer's date). I'm debating whether or not to stick with the wider tire or to go back to stock size.

Everyone here seems to like the wider tire than the stock tire, but doesn't this produce inaccurate speedometer readings (9.1% according to the tire calculator tool) and I believe produces a falsely high mileage reading as well? Also, I guess this would really make by MPGs look a lot better as well.

I want to use mine as a daily driver, not for autocross (well maybe.. who knows). So my question is do the wider tires help the 914 perform much better than the stock size tire under these driving conditions?

Before I drop lots of $$ of new tires, I'd like some feedback from the experts.
Thanks,
Don