One of the tires on my 2008 Legacy GT has a slow leak, and it has gotten worse enough in recent months that I'm to the point of taking some action.
Previously, the leak was slight enough, maybe 1 psi/wk, that I didn't bother with it. I've had the tires rotated, and always been one specific tire. I had the dealer test it in a water bath to find the leak, but they couldn't identify it at that point. I've driven about 8K miles since then though, and now it's leaking enough to trigger the indicator light every week (so maybe 7 psi/wk).
So now my I'm wondering whether I need to fix this by replacing all four tires. My tires have about 35K miles on them, so I suppose they have a decent amount of wear, but the mechanic said they had some life to them at my 30K maintenance. Should I just bite the bullet and replace them all? Or do I have other options?