A few things that can happen from not changing your fuel filter are: check engine and dash lights coming on, engine performance issues and breaking down of internal engine parts. Remember, if the internal parts of your engine start breaking down, there’s a chance it could lead to even more problems and more extensive damage. The best thing to do is change the fuel filter as soon as you know that’s the issue. This should really help keep your truck in the condition it needs to be to run smoothly.