I found it easier to grab the tank in the base at the top left of the first map and take it to the used car lot just across the bridge. You want to run over the cars head on or from the trunk, not from the side. The tank tends to flip the cars over if hit from the side and it's easy to get stuck. Trucks, vans and taller vehicles are much harder to climb over so I wouldn't bother with them. You can keep circling the car lot and cars will continuously respawn for you to crush.
When your tank's health is low, either wait until another tank shows up and carjack it or go back and get another from the base.
You can check progress by pressing
to going to the Statistics tab.
You can also combine this with the One Track Mind achievement where you need to destroy 100 tanks:
Here's a video: