How long will a 75c tank of gas last running up and down the street

lol, kinda hard to answer that question with the info you provided.

It depends on a lot of things but for a general answer 10-15 min.

my .18 only lasts about 7-8 min running up and down the street.

Two reasons:

a) Its an .18
b) The fuel i am using. I switched to Traxxass..... gargantuous mistake.

I have a heavy finger. So i would say no more than 10 minutes. So when you run out of fuel in the tank then you just pull the tab and refill it. Not that hard.