Hello, teachers!

Would you please tell me if these are everyday expressions, and are there other expressions?

1. This car runs 15 miles a liter (of gas).
2. This car runs 15 miles per liter.
3. This car runs 15 miles on one liter.
4. This car gets 15 miles to the liter.
5. This car gets 15 miles by the liter.

Thank you very much.
I like 3 and 4 best, especially 4. I like 5 least; I don't believe I've ever heard that one at all. 1 and 2 are borderline. You can change 'runs' to 'gets' in 1 and 2.

Concerning 5, "by the [quantity]" goes more with this sort of sentence:

Joe loves chocolate milk. He drinks it by the liter.

My neighbor is an avid gardener with a huge piece of property. He uses fertilizer by the ton!

Paper is sometimes sold by the ream.

We rarely mix litres and miles. You are mixing English and metric units.

1) This car gets 25 km per litre. - metric

2) [or you will sometimes see the metric expression as X litres per 100 km]

3) This car gets 25 miles per gallon. - English

Note for [1] and [3] that the numerator and denominator switch places between the two systems.

Students: Are you brave enough to let our tutors analyse your pronunciation?
I have also heard "This car does 15 kms to the liter." being used quite frequently. Is this a correct usage ?
Students: We have free audio pronunciation exercises.

That is quite common. I think it okay. It might be considered informal by some.

More formally, this car is rated at (or gets) 15 km per litre.