I recently had a flat tire (right front) on my 2008 Toyota Prius. The original donut spare, never used before, was used to replace it and I continued my 30 mile journey home, highway driving, before replacing the front tires. I was told that I could use the donut again. However, considering the age of the donut tire, would I be wise to replace it? I hesitate to ask the dealer or my tire store. How much should it cost? I don't feel confident in assessing the condition of the tire.
A donut spare is usually good for 50 miles at speeds of at most 50 mph.
You already did the 30 miles, presumably at about 50 mph because it was highway driving. So you can't expect the donut to last more than 20 further miles highway driving, considering tires age as a function of:
- Speed: you were driving probably at the maximum speed for the donut tire.
- Distance: you covered already 30 miles, which is 60% of the rated distance.
- Age: an unused tire shouldn't be put into use if over 6 years old, and a tire that's over 10 years old should be removed from use. Your donut is already 10 years old.
Is 20 miles enough for you to get from all possible places to the nearest tire shop? For me, I would replace the tire based on the list items (1), (2) and (3).