taking the guinea pig on a car vacation

Question
I hope you can help...  We are about to take our guinea pig on our annual trek to grandma's house- 18 hours away by car.  I have yet to find one human who even takes their pig on vacation, never mind for such a long trip.  He is such a part of our family that we couldn't bear to leave him with a sitter again this year, and I would like to be as prepared as possible, but I'm unsure of what to expect.  Vet says to bring all food and water from home.  Internet says not to leave in a closed up car (DUH!)  Please advise...

Answer
Take lots of goodies....be sure the "crate" isn't too big, if could cause him to get injured! The closed up car is a duh, but you would NOT believe how many ppl do that!! Are you taking his regular cage for while you are at grandma's?? Does he/or she have any special toys Such as a teddy bear, that they are particularly fond of?? take that too....

good luck...and let me know how the trip goes!!

Jess