The Urban Survivalist Guide says that one should keep their vehicle visually legal as to not attract attention of the authorities at a time when you least want them too - when transporting bodies - weapons for the underground, food for the freeloaders etc because sod's law will apply - you will get pulled for that illegal numberplate you have driven with for 30 thousand mile previously and risk blowing your whole gig.
THE WOLF: About the car, is there anything I need to know? Does it stall, does it make a lot of noise, does it smoke, is there gas in it, anything?
JULES: Aside from how it looks, the car's cool.
THE WOLF: Positive? Don't get me out on the road and I find out the brake lights don't work.
JULES: Hey man, as far as I know, da mother's tip-top.
:D
Okay the above is a bit of fun, but in my experience it best not to give *them* an excuse - that day you accidentally cut up a traffic cop on a roundabout and get pulled... good chance the smallest thing wrong with your ride will get picked up on. I have had my tyre pressures, wipers, screen washes, lights, horn all checked before - "Just routine winter check sir"