Best mileage: use 165/65R14 OEM Bridgestone RE92 tire (this is an all season tire but that category is a joke, more on this later)tubesguy said:
Best summer grip in dry and wet roads: 195/55R14 Toyo T1R or 185/60R14 Yokahama ES100
Best grip in snow and ice: Winter tires such as the 165/65R14 OEM sized Bridgestone Blizzak MZ-03
Best all season tire? These tires are a huge compromise in all conditions. They do not excel in any road condition. Some of the premium quality all season are the best at being quite, comfortable and last a long time, but they do this by sacrificing grip and mileage. IF you want the best mileage by all means buy the OEM RE92 but If you want another all season tire I cannot help you. My experience instructing advanced driving courses has turned me away from ever wanting to buy all season tires again.
Normad mentioned some interesting options from Nokian but i don't have experience with those specific tires.