Don,
what does that mean 'put their car up on blocks'? How much could they bootleg on one tank of gas? unless im misunderstanding..

 Urbanites had ration cards and were permitted to buy X gallons of gas. You were allocated a reasonable amount of gas if you were a doctor or a civic official, otherwise you were allocated so little it made more sense to jack the car up and set the axles on blocks of wood. This lifted the wheels off the ground and prevented damage to tires during an extended period of storage.

 Farmers were not rationed for gas. They could buy what they needed to work tractors etc. They could also buy more than they needed and sell the extra to city dwellers.

They basically put the car to pasture. Putting a block ( rock, wood, steel jack stand ) under each side of each axle and keeping the tires off the ground.  Get a buggy and push it to the nearest friendly farmer and get 10 to 20 gallons of unrationed gas or as much as your push cart tanks could carry. And go sell it to the folks that would otherwise be standing in line at the gas pumps.  

The BLACK MARKET that will crop up in every venue for everything that is in short supply, or even illegal.  Someone will have acess to a good steady supply and/or be able to trade for other items.