Given the following LINQ query:
from c in cars join r in repairs on c.VIN equals r.VIN ...
What kind of join does this perform?

By default, join/on/equals performs an inner join.

A cross join is a join of every element in the first sequence to every element in the second sequence to produce a Cartesian product, and no equals keyword is required.

A left outer join requires you to join all elements from the first (left side) sequence to the second sequence where there is equality, but all items in the first sequence are outputted even if there is no match to the second sequence.