Is there a difference between when to use one or the other? Both translate directly to fire truck.
This is an issue about 书面语(words that are used for writing articles) and 口语 (words that are usually used in oral Chinese)
The two words have the same meaning. However, 消防车 is more formal, it's used in most of the written materials. 救火车, on the other hand, is usually used in spoken Chinese, it's rarely used in formal documents.
As an example, 妻子 and 老婆 are both Chinese words for "wife". 妻子 is 书面语 while 老婆 is 口语.
I think they are same thing in most situations. But, in particular time ,the “消防车” ' range are bigger. In use,
"救火车" the name is called, for its reason -- directly to put off fire.
"消防车" is not only to do that, they can be used in other disaster situation, such as
- Earth Quake
In addition, we called "119" as "火警" when fire happens. But now, we call "119" for more difficulties : stuck in somewhere, lost, etc.