I drive a 2014 Prius Two. In the 14 months since I purchased the vehicle in October 2017, I have added 40,000 miles to it. (My work commute is rather long and also have been on several road trips over the past year). I am based out of a moderate-sized midwestern city and my daily work commute is 98% low-stress interstate cruising. Other, non-work-commute driving is a mix of interstate and city roads. The tires were new when I purchased the car. Michelin. Aside from keeping them filled with air and tire rotations during oil changes, I have had to do no maintenance on the tires since I've owned the car. How many more miles / how much longer do you think the tire life will be?
That number is best calculated by someone who knows the tread depth when the tires were new and the current tread depth. That should allow a good estimate. Anything else would be a guess, and probably a poor one. A tread depth gauge is a handy tool to have.
Step one: get a tread depth gauge, measure what you have left. Then, look up the new tire tread depth. Decide your mininum tread depth "comfort level", and for this I woudn't cheap out, would say 4/32" bare minimum, more if there's any possibility they'll encounter snow. Extrapolate from the above data. Let's say your new tread depth was 10/32", and you currently have 6/32", and your minumum tread will be 4/32". That's a "lfespan" of 6/32", and you've already eaten up 4/32". Then do a ratio equation (overkill but whatever): (This example practically falls into your lap.)
Welcome to Prius Chat. You don't want to run those interstates with minimum tread on your tires especially with the amount of driving you do especially on winter roads. There is a lot of good information by others. How much do you know about tires? Do you know where the wear bars are on the tires? Look at them, they are there for a visual reference. If you are getting close to them you will have time to start looking for new tires. Drive safe.
So many variables. Generally you watch for threadwear or tire age rot except for the unexpected tire damage or uneven wear. You will be forced to replace your tires if the unexpected happens. There are many tire articles online: Threadwear - Rotate tires to maximize tire thread life https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=157 Tire Rot or Age Do You Really Need To Replace Those Tires? Uneven wear due to alignment or suspension 3 Ways to Maintain Better Steering Alignment - Veenstra's Auto Repair Punctures that cannot be patched or unrepairable leaks (I don't have any hyperlinks) How many miles you have left depends on which of the above happens first. Some drivers simply replace them when they subjectively realize the tires are starting to slip or don't get enough traction.
At the very least, your tires should have been rotated during that 40,000 miles; probably at least twice. Visit a tire store and have them inspected........and ask them to guess at how much you have left. Unless they were brand new when you got them, my guess would be that they are close to needing replacement NOW.
^ Yeah our OEM tires had plenty of tread left, but were nearing 10 years from manufacture date (there's a code stamped on side wall), and were getting pretty cracked, and a couple of "weird" bits: a short, zigzag split in between the tread on one, and an odd hole, not all the way through, on another. It was time, lol. Plus, one was plug-repaired, though that didn't worry me.
impossible to say. However I will suggest that you can further the life of your tires by rotating more often, if you are only rotating with oil changes every 10k (assuming you follow factory schedule) you can probably extend life by doing every 5k. Proper inflation helps as well. Other than that it just all depends on your specific situation. I drive about 75% interstate on my daily commute of 42 miles each way, and I got 60K out of the factory Bridgestone Ecopia tires. Could have gotten more but ended up changing them due to winter approaching and wanting to be safe. Had it been summer I could have easily gotten another 5 to 7k easily out out of them.
I do all highway driving and have gotten 65k out of each set of tires which, coincidentally, is close to the tread life warranty. Inflate and rotate.
