There are a few things I consider when I want to get a new car.
1. Is current car going to cost more to fix than it's worth.
2. What is the frequency of repairs? Within this is, how often have I been inconvenienced because of break downs? This can almost be given a cash value.
3. How much would a new car cost per month compared to current car?
Example - New car might have higher payment. But, have a warranty, get better gas mileage, be worth more, hold value more, etc.
This is wear I was when my '98 Grand Cherokee gave me problems.
I paid $3,000 for the thing. Within 1 year I had replaced a radiator, clutch fan, driver door(cost of door, repaint, install). Even still, it had A/C condensation still leaking inside after countless fixes. Uncomfortable, noisy, poor gas mileage.
Buying the GTP was a no brainer. More reliable. low payment. comfy. Came with a warranty. And fast to boot. Not to mention, the dealer gave me $3,000 for the jeep.