1. I just saw a dog chasing a car and that car WAS his owner's car.
2. 1. I just saw a dog chasing a car and that car IS his owner's car.
"I saw a dog chasing a car which belonged to its owner." That is what most British speakers of English might say. Both of your forms sound like "foreigner's English".
Note "its" because you do not know the sex of the dog. Most non-human creatures are referred to by "it" and "its" unless they are well-loved family pets or the sex is known for sure and is important to the conversation..
One should know the grammar rule known as Consequence of Tenses. If you use Past in the first part , you have to use the same in the second..
number one correct.
It is preferred to match tenses (the statements are true at the same time). The second clause could be used in the present tense if the statement is still true, of course. It would imply that the car was also the owner's car at the time of the chasing, or the statement would be "misleading". Something that might be used in a riddle to fool someone. the second statement could mean that the car was not the owner's car at the time of chasing even if the event "just" happened, but this would not be expected.
Try paraphrasing. What I saw was a car chased by its owner's dog. Then,there's your solution to the question. Almost borders on heuristic reasoning!
Either would be OK - the fact that something has JUST happened implies that the ownership of the car would still be current.
If you said: I once saw a dog chasing a car and that car WAS his owner's car. Then it would firmly be in the past. (However the endless repetition of car would be something to avoid.)
You saw the dog in the past and the car was his owners car at that time in the past so you may use was. If that car is still his owners car you may use is. Actually in the UK we would say neither. We would say "I just saw a dog chasing his owners car."
This is one of those cases where the strictly correct grammar sounds wrong. 2 is correct (unless the owner sold the car in the mean time), but 1 would be the most common usage.
1 is the correct word.
It would be more natural to say
‘I just saw a dog chasing a car and it was his owner's car’
In the US, anyway. Fyi
1 is correct !
It depends upon the current ownership of the vehicle which you described as being chased by the dog. Was it sold by the dogs owner and currently owned by someone else. In that case it WAS the owner's car. If it is currently owned by the dog's owner it IS his owner's car. Check the registration and vehicle title in order to choose the sentence which will be more proper in your description of the events concerning vehicle ownership in the recent chase.
number 2 because WAS refers to past tense in number 1, 2 is correct because just saw and IS refers to now or present.