Q:

What's the cheapest way to discover all dealerships?

I found the map beneath in this Reddit post (that lists the dealerships too), and I know that it's outmoded, as v1.34.0.5 added states. Dealers are listed on this forum too.
I started playing ATS yesterday, and have merely the one default tractor unit.

Can I drive to dealers in merely the lone tractor unit (without a semi-trailer)?
If I must drive to dealers in the whole semi-trailer truck, how? 

A:

The ATS Wikia Dealers page seems to be more updated than the Reddit post. It even includes Oregon.
What I did was follow the Wikia page to find the cities where dealers are located, and just take jobs that would take me to those cities. You can drive to dealers with just the truck without a hitched trailer. Once I completed my job in the city with an undiscovered dealer, I would drive around with just the truck.
You can also stop by the dealer before you complete the job (i.e. with the trailer attached). Just make sure you leave enough time to finish your delivery.
Hope this helps.

