Hi! If you can accommodate a small cage or large cardboard box in your car so he can have round the clock access to soft hay and fresh water as well as a soft hidey (soft in case of a sudden break), it is doable. Ideally, you want be able to clean him out once a day (take fresh bedding and refuse/bin bags with you). Your piggy can survive for that long in fairly constricted surroundings if that means that you don't have to give him up, which would be even more upsetting for him!
Two of my permanent fosters and their friends, who have gone on to other places, have come in cat carriers all the way from Jersey (which is a Channel Island close to France) in a 3-4 day emergency trip via a (rough) ferry crossing, several car journeys and a leg on the train, but they have all survived well, even the 9 year old (who went on to live for a few more months!) and the piggy with the weight loss (who made a full recovery). #
As you can plan ahead, I am sure that your trip will go more smoothly! If you can, let him get used to and comfy with his travel cage and/or being in a car beforehand.
Here are our travel tips:
http://www.theguineapigforum.co.uk/threads/travelling-with-guinea-pigs.109071/
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