I like that word savvy and learned it about 1 year and a 1/2 ago even though I’ve been speaking English for 10 years on a daily basis.

I’ve never put the dots together savoir / savvy.
So, I had to check the info and source. Here is what I found:

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I - SAVVY
The Concise Oxford Dictionary of English Etymology

savvy know. XVIII. Negro and Pidgin Eng., repr. the first word of Sp. sabe usted you know (saber :- Rom. *sap?re, for L. sapere know; see SAPIENT).
Hence sb. practical sense, nouns XVIII.
Find more facts and information related to the .
© The Concise Oxford Dictionary of English Etymology 1996, originally published by Oxford University Press 1996.

Source: http://www.encyclopedia.com
Made possible by HighBeam Research, Inc.

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II - SAVVY
Online Etymology Dictionary

1785, as a noun, “practical sense, intelligence;” also a verb, “to know, to understand;” W. Indies pidgin borrowing of Fr. savez(-vous)? “do you know?” or Sp. sabe (usted) “you know,” both from V.L. *sapere, from L. sapere “be wise, be knowing” (see sapient). The adj. is first recorded 1905, from the noun.

Source: http://www.etymonline.com
Author: Douglas Harper

I actually like that word savvy! I’ve never put the dots together savoir / savvy.
I learned about it about a 1 year and 1/2 ago eventhough I’ve been speaking English fluently on daily basis for 10 years!
I had to check the info and source. So that is what I found:
————————————————————————————————–
SAVVY
The Concise Oxford Dictionary of English Etymology

savvy know. XVIII. Negro and Pidgin Eng., repr. the first word of Sp. sabe usted you know (saber :- Rom. *sap?re, for L. sapere know; see SAPIENT).
Hence sb. practical sense, nouns XVIII.
Find more facts and information at The Concise Oxford Dictionary of English Etymology 1996, originally published by Oxford University Press 1996.

Source: http://www.encyclopedia.com
made possible by Highbeam Research.
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SAVVY
http://www.etymonline.com

1785, as a noun, “practical sense, intelligence;” also a verb, “to know, to understand;” W. Indies pidgin borrowing of Fr. savez(-vous)? “do you know?” or Sp. sabe (usted) “you know,” both from V.L. *sapere, from L. sapere “be wise, be knowing” (see sapient). The adj. is first recorded 1905, from the noun.

Source: http://www.etymonline.com Author: Douglas Harper

“Tu veux qu’on fasse un tour ? ” (faire un tour)
is an invitation for a ride and or for a walk. You may have to ask for more precision : en voiture ? (by car) à pied ? (on foot).
And yes this expression is really common. this is the one that we use everyday:

- On va faire un tour ?
- Allons faire un tour !
- Je vais faire un tour.
- Elles sont parties faire un tour.

About the 2CV, I have no idea it there is an equivalent.