You don't need it - drink lots of water.
As well as reducing engine power, it also considerably increases fuel consumption. Both major issues in the desert.
I'm not sure how well the Parisian chick would do getting out of her AC Toyota to get digging in the sand either - that's certainly shock treatment to the system.
Also, if you have to keep the windows closed all the time, you're not going to have much interaction with the locals on your route.
In the words of Robin Williams in 'Good Morning Vietnam':
"You got a window, open it!".
Sam.
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