We also would say: "Я продав два авта." for "I sold two cars."
At first, I also was confused with the term 'машина' in 'new' Ukrainian. As I (any many others who use the term 'авто' for 'car') consider the word 'машина' just a general term for ANY Machine. An 'авто/автомобіль' is more specific, and everyone KNOWS what it is.
Years ago, someone asked me : "Чи ви маєте машину?" (and I was not aware of the 'new addition' to the Ukrainian vocabulary), I'd ask the person: "Яка машина? Про яку машину ви говорити? Я маю багато всяких машин!" LOL
The person replied: "Та що іди! (*Sorry I don't have the letter 'yi' in my Ukie font.) "The one that drives."
I repied: "Там є всякі машини що *'ідять'. Прошу бути більше спесифічно!" ("There are various machines that 'drive/go'. Please be more specific!")
Only until the person pointed to an actual motor vehicle (car), I understood what they meant.
They, also did not realize that in Canada we use the 'older' Ukrainian words our ancestors came here with. So we both laughed and learned from eachother! All is well! :)