Of course rather than useing it only in the search you could make the sybnonyms table visible on a page... If there is input into this synonyms table it doesn't seem really hard to make it visible...you just have to find the right place to put it...

To organize them better than on make and model...I don't think there is a better way. However with each car you could put up a link to the synonym table for that specified car, it would be a better user interface and would be more easy to find the same cars, which have a different name in another country.

So what I am saying actually is to put up a standard link with each car description, pointing to the synonyms of the car.

auto replacement is in in my opinion a different subject, it is just an help on the search to find certain makes that are also common known as another name.

There is a slight difference between that and an official other name supplied by the manufacturer....