.......... So all in all, i'd say it is scam. sorry......
Not really. I don't know about today, but back in the '60's it was a
popular practice.  Even before that my dad used to purge and fill with
nitrogen in his '53 Chrysler Hemi. (got the bottles of nitrogen filled
for free, he did repair work for the local dry ice plant, Liquid
Carbonic.  They also produced liquid air and oxygen in that plant).  Use
of dry nitrogen is common in good optical instruments, especially if
intended for outdoor use.  If you have a high end rifle scope or pair of
binoculars, there are special ports built into them for purging and
filling with nitrogen: no moisture, no condensation and internal
fogging. (I'm an optics nut and worked for the firm with the largest
binocular repair center on the west coast for five plus years, watched
this being done on a regular basis)
As to the value to the average driver??  Probably nearly nill and very
difficult measure any benefit.