The odometer reads 30k miles...with the types of cars I deal with this ALWAYS means 130k.  I asked my grandpa and he thinks it is really 30k miles...but he is an optimistic guy and I don't trust his memory too much.

According to my grandpa, he bought the car used from a couple old ladies for my aunt to use in college she drove it back in forth to college "a couple times a year" and around her college town.  Then my uncle drove it in highschool for a couple years before getting a different car for college.

The engine is caked in oil sludge and is all brown, the car is Rusty (but it was driven in Wisconsin).

What are the "signs" I should look for to make an estimated guess on the miles...other things in the car to look at?  Or would it be impossible to even guess.