Offer your thoughts or opinion on the input financial query or topic using your financial background.

Buy tires and keep car for 12-36 months, or replace car now? 
It depends how detailed you want to get in your calculation, but fundamentally, 1K < 25K.   On a very basic level, divide the cost (less what you sell it for) by the time you'll have the car for.  If you junk it, $1K/12 month = $83/month to buy tires to have a car for a year. If you sell it for $1K, then it become $0/month.  (Plus other maintenance, etc..., obviously). If you pay 25K and keep the new car for ten years and sell it for nothing, it becomes roughly $208/month (plus maintenance). If you want to get more accurate, there are a lot of variables you can take into account--time cost of money, financing, maintenance costs of different vehicle types, etc...