"on Mondays" v. "on Monday" with the adverb, "always" [closed]

Are all of these correct?

1. I wash my car on Mondays.
2. I always wash my car on Monday.
3. I always wash my car on Mondays.

I know #1 is correct, and it means every Monday. However, I'm not sure if #2 is correct. If we use the adverb "always," is it necessary to put the "s" at the end of "Monday"? I think for #3 the use of "always" adds emphasis to the fact that it is every Monday.

While all three are correct, the use of both always and the plural Mondays in example 3 seems a bit redundant. The first two would be more common and interchangeable.

SUPPLEMENT: As noted in the comments, there is a degree of ambiguity as to whether these sentences are inteded to mean that the car is washed every Monday, or only that, when it is washed, it would be on a Monday, but not necessarily every week.

To avoid ambiguity, you could say

I wash my car every Monday.

or

Whenever I wash my car, it's on a Monday.