If you wish to avoid using the term "high-pollution car," there are a few alternative synonyms to use instead. "Polluting car" is one option, while "emitting car" is another. Another possibility is the phrase "vehicle with high emissions." You might also describe the car as a "high-emitting vehicle" or simply as a "high-emission car." Another option is to use more specific language that describes the type of pollution being produced, such as "smog-producing car" or "carbon-emitting vehicle." Whatever term you choose, it is important to acknowledge the environmental impact of high-polluting cars and work towards reducing emissions.