Over the years, a high percentage of highway breakdowns involve:
-
Belts
-
Hoses
-
Tires.
The other issues, such as timing belts and/or water pump are of course possible, but check out these three and your odds of failure go way down.
I create a lot of hostility with this, but IMO you should check all external lights. A bad light is used today by many law enforcement agencies as an excuse to stop you, and try to browbeat you into letting them search your car in hopes of finding something wrong and confiscating your car. Don’t speed, not even 1 mph, and make sure those lights are good and that will reduce slightly the chances of getting stopped. (I say it that way because some are simply fabricating probable cause to stop you. It happened to my son and me in a two hour period last summer, in two different states.)
The US Supreme Court ruled in KNOWLES V. IOWA, in the late 90’s, that they do not have the right to do a complete search of a car or a trivial traffic stop. But, they lie.
I hope I don’t need to warn you that it is not a good idea to have anything illegal with you.